Serving node relocating method in wireless communication system and device for same

ABSTRACT

Disclosed are a serving node relocating method in a wireless communication system and a device for same. In detail, a method for relocating, by a first serving node, a serving node in a wireless communication system can include: receiving a tracking area update (TAU) request message from a terminal; transmitting an update location request to a home subscriber server (HSS), when the first serving node having received the TAU request message is different from a second serving node that is an old node; and transmitting an update location message to a service capability exposure function (SCEF), when the first serving node is different from the second serving node that is the old node and a connection for transmitting/receiving non-internet protocol (non-IP) data via the SCEF is configured in the terminal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage filing under 35 U.S.C. 371 ofInternational Application No. PCT/KR2016/012700, filed on Nov. 4, 2016,which claims the benefit of U.S. Provisional Application No. 62/250,515,filed on Nov. 4, 2015, the contents of which are all hereby incorporatedby reference herein in their entirety.

TECHNICAL FIELD

The present invention relates to a wireless communication system and,more specifically, to a method for performing/supporting relocation of aserving node and a device supporting the same.

BACKGROUND ART

Mobile communication systems have been developed to provide voiceservices, while guaranteeing user activity. Service coverage of mobilecommunication systems, however, has extended even to data services, aswell as voice services, and currently, an explosive increase in traffichas resulted in shortage of resource and user demand for a high speedservices, requiring advanced mobile communication systems.

The requirements of the next-generation mobile communication system mayinclude supporting huge data traffic, a remarkable increase in thetransfer rate of each user, the accommodation of a significantlyincreased number of connection devices, very low end-to-end latency, andhigh energy efficiency. To this end, various techniques, such as smallcell enhancement, dual connectivity, massive Multiple Input MultipleOutput (MIMO), in-band full duplex, non-orthogonal multiple access(NOMA), supporting super-wide band, and device networking, have beenresearched.

DISCLOSURE Technical Problem

An object of the present invention is to propose a serving noderelocating method for smoothly performing a mobile terminated call evenwhen a serving node (e.g., mobility management entity (MME), servinggeneral packet radio service (GPRS) supporting node (SGSN) or the like)of a UE is changed during transmission of small data (e.g., non-IP data)using a service capability exposure function (SCEF).

It will be appreciated by persons skilled in the art that the objectsthat could be achieved with the present invention are not limited towhat has been particularly described hereinabove and the above and otherobjects that the present invention could achieve will be more clearlyunderstood from the following detailed description.

Technical Solution

In one aspect of the present invention, a method for relocating, by afirst serving node, a serving node in a wireless communication systemmay include: receiving a tracking area update (TAU) request message froma UE; transmitting an update location request to a home subscriberserver (HSS) when the first serving node having received the TAU requestmessage is different from a second serving node that is an old node; andtransmitting an update location message to a service capability exposurefunction (SCEF) when the first serving node is different from the secondserving node that is the old node and a connection fortransmitting/receiving non-Internet protocol (non-IP) data via the SCEFis configured for the UE.

In another aspect of the present invention, a first serving node forrelocating a serving node in a wireless communication system mayinclude: a communication module for transmitting/receiving signals; anda processor for controlling the communication module, wherein theprocessor is configured: to receive a tracking area update (TAU) requestmessage from a UE; to transmit an update location request to a homesubscriber server (HSS) when a first serving node having received theTAU request message is different from a second serving node that is anold node; and to transmit an update location message to a servicecapability exposure function (SCEF) when the first serving node havingreceived the TAU request message is different from the second servingnode that is the old node and a connection for transmitting/receivingnon-Internet protocol (non-IP) data via the SCEF is configured for theUE.

Preferably, when the first serving node is different from the secondserving node that is the old node, a context request message may betransmitted to the second serving node in order to retrieve a UEcontext, a context response message including the UE context may bereceived from the second serving node in response to the context requestmessage, and whether the connection for transmitting/receiving non-IPdata is configured for the UE may be determined using the UE context.

Preferably, when the type of a PDN connection between the UE and apacket data network (PDN) is non-IP, and subscription informationcorresponding to the PDN connection includes an Invoke SCEF Selectionindicator, it may be determined that the connection fortransmitting/receiving non-IP data via the SCEF is configured for theUE.

Preferably, when notification to the SCEF for a relocation of theserving node is configured in the first serving node, the updatelocation message may be transmitted to the SCEF.

Preferably, an update location acknowledgement message for acknowledginglocation update may be received from the SCEF in response to the updatelocation message.

Preferably, when non-IP data to be transmitted to the UE is receivedfrom the SCEF, the non-IP data may be included in a non-access stratumpacket data unit (NAS PDU) and transmitted it to the UE.

Advantageous Effects

According to embodiments of the present invention, a mobile terminatedcall can be smoothly transmitted without being lost because the SCEF canrecognize the most recent serving node.

According to embodiments of the present invention, signaling overheadcan be reduced because the SCEF may not send a query about the locationof a serving node (i.e., routing information) to a home subscriberserver (HSS) when a mobile terminated call is transmitted.

It will be appreciated by persons skilled in the art that the effectsthat can be achieved with the present invention are not limited to whathas been particularly described hereinabove and other advantages of thepresent invention will be more clearly understood from the followingdetailed description.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the present invention and constitute a part ofspecifications of the present invention, illustrate embodiments of thepresent invention and together with the corresponding descriptions serveto explain the principles of the present invention.

FIG. 1 is a diagram schematically exemplifying an evolved packet system(EPS) to which the present invention can be applied.

FIG. 2 illustrates an example of evolved universal terrestrial radioaccess network structure to which the present invention can be applied.

FIG. 3 exemplifies a structure of E-UTRAN and EPC in a wirelesscommunication system to which the present invention can be applied.

FIG. 4 illustrates a structure of a radio interface protocol between aUE and E-UTRAN in a wireless communication system to which the presentinvention can be applied.

FIG. 5 is a diagram schematically showing a structure of a physicalchannel in a wireless communication system to which the presentinvention may be applied.

FIG. 6 is a diagram for describing a contention based random accessprocedure in a wireless communication system to which the presentinvention may be applied.

FIG. 7 is a diagram schematically showing an attach procedure in awireless communication system to which the present invention may beapplied.

FIG. 8 is a diagram schematically showing a PDN connectivity procedurein a wireless communication system to which the present invention may beapplied.

FIG. 9 is a diagram showing an architecture for machine-typecommunication (MTC) in a wireless communication system to which thepresent invention may be applied.

FIG. 10 is a diagram showing an architecture for service capabilityexposure in a wireless communication system to which the presentinvention may be applied.

FIG. 11 is a diagram showing an end-to-end small data flow in a wirelesscommunication system to which the present invention may be applied.

FIG. 12 shows a cellular IoT network architecture proposed for efficientnon-IP small data transmission through an SCEF in a wirelesscommunication system to which the present invention may be applied.

FIG. 13 shows a procedure of configuring and deleting a monitoring eventthrough an HSS in a wireless communication system to which the presentinvention may be applied.

FIG. 14 shows an MO small data transmission procedure in a wirelesscommunication system to which the present invention may be applied.

FIG. 15 shows an MT small data transmission procedure in a wirelesscommunication system to which the present invention may be applied.

FIG. 16 shows a link setup process for transmitting UL/DL data (i.e.,non-IP data) through an MME and an SCEF in a wireless communicationsystem to which the present invention may be applied.

FIG. 17 shows an NIDD configuration procedure in a wirelesscommunication system to which the present invention may be applied.

FIG. 18 shows a T6a connection establishment procedure in a wirelesscommunication system to which the present invention may be applied.

FIG. 19 shows a mobile terminated NIDD procedure in a wirelesscommunication system to which the present invention may be applied.

FIG. 20 shows a tracking area update procedure in a wirelesscommunication system to which the present invention may be applied.

FIG. 21 is a diagram showing a serving node relocating method accordingto an embodiment of the present invention.

FIG. 22 is a diagram showing a serving node relocating method accordingto an embodiment of the present invention.

FIG. 23 is a diagram showing a serving node relocating method accordingto an embodiment of the present invention.

FIG. 24 is a block diagram of a communication device according to anembodiment of the present invention.

FIG. 25 is a block diagram of a communication device according to anembodiment of the present invention.

MODE FOR INVENTION

In what follows, preferred embodiments according to the presentinvention will be described in detail with reference to appendeddrawings. The detailed descriptions provided below together withappended drawings are intended only to explain illustrative embodimentsof the present invention, which should not be regarded as the soleembodiments of the present invention. The detailed descriptions belowinclude specific information to provide complete understanding of thepresent invention. However, those skilled in the art will be able tocomprehend that the present invention can be embodied without thespecific information.

For some cases, to avoid obscuring the technical principles of thepresent invention, structures and devices well-known to the public canbe omitted or can be illustrated in the form of block diagrams utilizingfundamental functions of the structures and the devices.

A base station in this document is regarded as a terminal node of anetwork, which performs communication directly with a UE. In thisdocument, particular operations regarded to be performed by the basestation may be performed by an upper node of the base station dependingon situations. In other words, it is apparent that in a networkconsisting of a plurality of network nodes including a base station,various operations performed for communication with a UE can beperformed by the base station or by network nodes other than the basestation. The term Base Station (BS) can be replaced with a fixedstation, Node B, evolved-NodeB (eNB), Base Transceiver System (BTS), orAccess Point (AP). Also, a terminal can be fixed or mobile; and the termcan be replaced with User Equipment (UE), Mobile Station (MS), UserTerminal (UT), Mobile Subscriber Station (MSS), Subscriber Station (SS),Advanced Mobile Station (AMS), Wireless Terminal (WT), Machine-TypeCommunication (MTC) device, Machine-to-Machine (M2M) device, orDevice-to-Device (D2D) device.

In what follows, downlink (DL) refers to communication from a basestation to a terminal, while uplink (UL) refers to communication from aterminal to a base station. In downlink transmission, a transmitter canbe part of the base station, and a receiver can be part of the terminal.Similarly, in uplink transmission, a transmitter can be part of theterminal, and a receiver can be part of the base station.

Specific terms used in the following descriptions are introduced to helpunderstanding the present invention, and the specific terms can be usedin different ways as long as it does not leave the technical scope ofthe present invention.

The technology described below can be used for various types of wirelessaccess systems based on Code Division Multiple Access (CDMA), FrequencyDivision Multiple Access (FDMA), Time Division Multiple Access (TDMA),Orthogonal Frequency Division Multiple Access (OFDMA), Single CarrierFrequency Division Multiple Access (SC-FDMA), or Non-Orthogonal MultipleAccess (NOMA). CDMA can be implemented by such radio technology asUniversal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA can beimplemented by such radio technology as Global System for Mobilecommunications (GSM), General Packet Radio Service (GPRS), or EnhancedData rates for GSM Evolution (EDGE). OFDMA can be implemented by suchradio technology as the IEEE 802.11 (Wi-Fi), the IEEE 802.16 (WiMAX),the IEEE 802-20, or Evolved UTRA (E-UTRA). UTRA is part of the UniversalMobile Telecommunications System (UMTS). The 3rd Generation PartnershipProject (3GPP) Long Term Evolution (LTE) is part of the Evolved UMTS(E-UMTS) which uses the E-UTRA, employing OFDMA for downlink and SC-FDMAfor uplink transmission. The LTE-A (Advanced) is an evolved version ofthe 3GPP LTE system.

Embodiments of the present invention can be supported by standarddocuments disclosed in at least one of wireless access systems includingthe IEEE 802, 3GPP, and 3GPP2 specifications. In other words, among theembodiments of the present invention, those steps or parts omitted forthe purpose of clearly describing technical principles of the presentinvention can be supported by the documents above. Also, all of theterms disclosed in this document can be explained with reference to thestandard documents.

To clarify the descriptions, this document is based on the 3GPPLTE/LTE-A, but the technical features of the present invention are notlimited to the current descriptions.

Terms used in this document are defined as follows.

Universal Mobile Telecommunication System (UMTS): the 3rd generationmobile communication technology based on GSM, developed by the 3GPP

Evolved Packet System (EPS): a network system comprising an EvolvedPacket Core (EPC), a packet switched core network based on the InternetProtocol (IP) and an access network such as the LTE and UTRAN. The EPSis a network evolved from the UMTS.

NodeB: the base station of the UMTS network. NodeB is installed outsideand provides coverage of a macro cell.

eNodeB: the base station of the EPS network. eNodeB is installed outsideand provides coverage of a macro cell.

User Equipment (UE): A UE can be called a terminal, Mobile Equipment(ME), or Mobile Station (MS). A UE can be a portable device such as anotebook computer, mobile phone, Personal Digital Assistant (PDA), smartphone, or a multimedia device; or a fixed device such as a PersonalComputer (PC) or vehicle-mounted device. The term UE may refer to an MTCterminal in the description related to MTC.

IP Multimedia Subsystem (IMS): a sub-system providing multimediaservices based on the IP

International Mobile Subscriber Identity (IMSI): a globally uniquesubscriber identifier assigned in a mobile communication network

Machine Type Communication (MTC): communication performed by machineswithout human intervention. It may be called Machine-to-Machine (M2M)communication.

MTC terminal (MTC UE or MTC device): a terminal (for example, a vendingmachine, meter, and so on) equipped with a communication functionoperating through a mobile communication network(For example,communicating with an MTC server via a PLMN) and performing an MTCfunction

MTC server: a server on a network managing MTC terminals. It can beinstalled inside or outside a mobile communication network. It canprovide an interface through which an MTC user can access the server.Also, an MTC server can provide MTC-related services to other servers(in the form of Services Capability Server (SCS)) or the MTC serveritself can be an MTC Application Server.

(MTC) application: services (to which MTC is applied) (for example,remote metering, traffic movement tracking, weather observation sensors,and so on)

(MTC) Application Server: a server on a network in which (MTC)applications are performed

MTC feature: a function of a network to support MTC applications. Forexample, MTC monitoring is a feature intended to prepare for loss of adevice in an MTC application such as remote metering, and low mobilityis a feature intended for an MTC application with respect to an MTCterminal such as a vending machine.

MTC User (MTC User): The MTC user uses the service provided by the MTCserver.

MTC subscriber: an entity having a connection relationship with anetwork operator and providing services to one or more MTC terminals.

MTC group: an MTC group shares at least one or more MTC features anddenotes a group of MTC terminals belonging to MTC subscribers.

Services Capability Server (SCS): an entity being connected to the 3GPPnetwork and used for communicating with an MTC InterWorking Function(MTC-IWF) on a Home PLMN (HPLMN) and an MTC terminal. The SCS providesthe capability for use by one or more MTC applications.

External identifier: a globally unique identifier used by an externalentity (for example, an SCS or an Application Server) of the 3GPPnetwork to indicate (or identify) an MTC terminal (or a subscriber towhich the MTC terminal belongs). An external identifier comprises adomain identifier and a local identifier as described below.

Domain identifier: an identifier used for identifying a domain in thecontrol region of a mobile communication network service provider. Aservice provider can use a separate domain identifier for each serviceto provide an access to a different service.

Local identifier: an identifier used for deriving or obtaining an

International Mobile Subscriber Identity (IMSI). A local identifiershould be unique within an application domain and is managed by a mobilecommunication network service provider.

Radio Access Network (RAN): a unit including a Node B, a Radio NetworkController (RNC) controlling the Node B, and an eNodeB in the 3GPPnetwork. The RAN is defined at the terminal level and provides aconnection to a core network.

Home Location Register (HLR)/Home Subscriber Server (HSS): a databaseprovisioning subscriber information within the 3GPP network. An HSS canperform functions of configuration storage, identity management, userstate storage, and so on.

RAN Application Part (RANAP): an interface between the RAN and a node incharge of controlling a core network (in other words, a MobilityManagement Entity (MME)/Serving GPRS (General Packet Radio Service)Supporting Node (SGSN)/Mobile Switching Center (MSC)).

Public Land Mobile Network (PLMN): a network formed to provide mobilecommunication services to individuals. The PLMN can be formed separatelyfor each operator.

Non-Access Stratum (NAS): a functional layer for exchanging signals andtraffic messages between a terminal and a core network at the UMTS andEPS protocol stack. The NAS is used primarily for supporting mobility ofa terminal and a session management procedure for establishing andmaintaining an IP connection between the terminal and a PDN GW.

Service Capability Exposure Function (SCEF): An entity within the 3GPParchitecture for service capability exposure that provides a means forsecurely exposing services and capabilities provided by 3GPP networkinterfaces.

In what follows, the present invention will be described based on theterms defined above.

Overview of System to Which the Present Invention May be Applied

FIG. 1 illustrates an Evolved Packet System (EPS) to which the presentinvention can be applied.

The network structure of FIG. 1 is a simplified diagram restructuredfrom an Evolved Packet System (EPS) including Evolved Packet Core (EPC).

The EPC is a main component of the System Architecture Evolution (SAE)intended for improving performance of the 3GPP technologies. SAE is aresearch project for determining a network structure supporting mobilitybetween multiple heterogeneous networks. For example, SAE is intended toprovide an optimized packet-based system which supports various IP-basedwireless access technologies, provides much more improved datatransmission capability, and so on.

More specifically, the EPC is the core network of an IP-based mobilecommunication system for the 3GPP LTE system and capable of supportingpacket-based real-time and non-real time services. In the existingmobile communication systems (namely, in the 2nd or 3rd mobilecommunication system), functions of the core network have beenimplemented through two separate sub-domains: a Circuit-Switched (CS)sub-domain for voice and a Packet-Switched (PS) sub-domain for data.However, in the 3GPP LTE system, an evolution from the 3rd mobilecommunication system, the CS and PS sub-domains have been unified into asingle IP domain. In other words, in the 3GPP LTE system, connectionbetween UEs having IP capabilities can be established through anIP-based base station (for example, eNodeB), EPC, and application domain(for example, IMS). In other words, the EPC provides the architectureessential for implementing end-to-end IP services.

The EPC comprises various components, where FIG. 1 illustrates part ofthe EPC components, including a Serving Gateway (SGW or S-GW), PacketData Network Gateway (PDN GW or PGW or P-GW), Mobility Management Entity(MME), Serving GPRS Supporting Node (SGSN), and enhanced Packet DataGateway (ePDG).

The SGW operates as a boundary point between the Radio Access Network(RAN) and the core network and maintains a data path between the eNodeBand the PDN GW. Also, in case the UE moves across serving areas by theeNodeB, the SGW acts as an anchor point for local mobility. In otherwords, packets can be routed through the SGW to ensure mobility withinthe E-UTRAN (Evolved-UMTS (Universal Mobile Telecommunications System)Terrestrial Radio Access Network defined for the subsequent versions ofthe 3GPP release 8). Also, the SGW may act as an anchor point formobility between the E-UTRAN and other 3GPP networks (the RAN definedbefore the 3GPP release 8, for example, UTRAN or GERAN (GSM (GlobalSystem for Mobile Communication)/EDGE (Enhanced Data rates for GlobalEvolution) Radio Access Network).

The PDN GW corresponds to a termination point of a data interface to apacket data network. The PDN GW can support policy enforcement features,packet filtering, charging support, and so on. Also, the PDN GW can actas an anchor point for mobility management between the 3GPP network andnon-3GPP networks (for example, an unreliable network such as theInterworking Wireless Local Area Network (I-WLAN) or reliable networkssuch as the Code Division Multiple Access (CDMA) network and WiMax).

In the example of a network structure as shown in FIG. 1, the SGW andthe PDN GW are treated as separate gateways; however, the two gatewayscan be implemented according to single gateway configuration option.

The MME performs signaling for the UE's access to the network,supporting allocation, tracking, paging, roaming, handover of networkresources, and so on; and control functions. The MME controls controlplane functions related to subscribers and session management. The MMEmanages a plurality of eNodeBs and performs signaling of theconventional gateway's selection for handover to other 2G/3G networks.Also, the MME performs such functions as security procedures,terminal-to-network session handling, idle terminal location management,and so on.

The SGSN deals with all kinds of packet data including the packet datafor mobility management and authentication of the user with respect toother 3GPP networks (for example, the GPRS network).

The ePDG acts as a security node with respect to an unreliable, non-3GPPnetwork (for example, I-WLAN, WiFi hotspot, and so on).

As described with respect to FIG. 1, a UE with the IP capability canaccess the IP service network (for example, the IMS) that a serviceprovider (namely, an operator) provides, via various components withinthe EPC based not only on the 3GPP access but also on the non-3GPPaccess.

Also, FIG. 1 illustrates various reference points (for example, S1-U,S1-MME, and so on). The 3GPP system defines a reference point as aconceptual link which connects two functions defined in disparatefunctional entities of the E-UTAN and the EPC. Table 1 below summarizesreference points shown in FIG. 1.

In addition to the examples of FIG. 1, various other reference pointscan be defined according to network structures.

TABLE 1 Reference point Description S1-MME Reference point for thecontrol plane protocol between E-UTRAN and MME S1-U Reference pointbetween E-UTRAN and Serving GW for the per bearer user plane tunnelingand inter eNodeB path switching during handover S3 It enables user andbearer information exchange for inter 3GPP access network mobility inidle and/or active state. This reference point can be used intra-PLMN orinter-PLMN (e.g. in the case of Inter-PLMN HO). S4 It provides relatedcontrol and mobility support between GPRS core and the 3GPP anchorfunction of Serving GW. In addition, if direct tunnel is notestablished, it provides the user plane tunneling. S5 It provides userplane tunneling and tunnel management between Serving GW and PDN GW. Itis used for Serving GW relocation due to UE mobility if the Serving GWneeds to connect to a non-collocated PDN GW for the required PDNconnectivity. S11 Reference point for the control plane protocol betweenMME and SGW SGi It is the reference point between the PDN GW and thepacket data network. Packet data network may be an operator externalpublic or private packet data network or an intra- operator packet datanetwork (e.g., for provision of IMS services). This reference pointcorresponds to Gi for 3GPP accesses.

Among the reference points shown in FIG. 1, S2 a and S2 b corresponds tonon-3GPP interfaces. S2a is a reference point which provides reliable,non-3GPP access, related control between PDN GWs, and mobility resourcesto the user plane. S2 b is a reference point which provides relatedcontrol and mobility resources to the user plane between ePDG and PDNGW.

FIG. 2 illustrates one example of an Evolved Universal Terrestrial RadioAccess Network (E-UTRAN) to which the present invention can be applied.

The E-UTRAN system is an evolved version of the existing UTRAN system,for example, and is also referred to as 3GPP LTE/LTE-A system.Communication network is widely deployed in order to provide variouscommunication services such as voice (e.g., Voice over Internet Protocol(VoIP)) through IMS and packet data.

Referring to FIG. 2, E-UMTS network includes E-UTRAN, EPC and one ormore UEs. The E-UTRAN includes eNBs that provide control plane and userplane protocol, and the eNBs are interconnected with each other by meansof the X2 interface.

The X2 user plane interface (X2-U) is defined among the eNBs. The X2-Uinterface provides non-guaranteed delivery of the user plane Packet DataUnit (PDU). The X2 control plane interface (X2-CP) is defined betweentwo neighboring eNBs. The X2-CP performs the functions of contextdelivery between eNBs, control of user plane tunnel between a source eNBand a target eNB, delivery of handover-related messages, uplink loadmanagement, and so on.

The eNB is connected to the UE through a radio interface and isconnected to the Evolved Packet Core (EPC) through the S1 interface.

The S1 user plane interface (S1-U) is defined between the eNB and theServing Gateway (S-GW). The S1 control plane interface (S1-MME) isdefined between the eNB and the Mobility Management Entity (MME). The S1interface performs the functions of EPS bearer service management,non-access stratum (NAS) signaling transport, network sharing, MME loadbalancing management, and so on. The S1 interface supportsmany-to-many-relation between the eNB and the MME/S-GW.

The MME may perform various functions such as NAS signaling security,Access Stratum (AS) security control, Core Network (CN) inter-nodesignaling for supporting mobility between 3GPP access network, IDLE modeUE reachability (including performing paging retransmission andcontrol), Tracking Area Identity (TAI) management (for UEs in idle andactive mode), selecting PDN GW and SGW, selecting MME for handover ofwhich the MME is changed, selecting SGSN for handover to 2G or 3G 3GPPaccess network, roaming, authentication, bearer management functionincluding dedicated bearer establishment, Public Warning System (PWS)(including Earthquake and Tsunami Warning System (ETWS) and CommercialMobile Alert System (CMAS), supporting message transmission and so on.

FIG. 3 exemplifies a structure of E-UTRAN and EPC in a wirelesscommunication system to which the present invention can be applied.

Referring to FIG. 3, an eNB may perform functions of selecting gateway(e.g., MME), routing to gateway during radio resource control (RRC) isactivated, scheduling and transmitting broadcast channel (BCH), dynamicresource allocation to UE in uplink and downlink, mobility controlconnection in LTE_ACTIVE state. As described above, the gateway in EPCmay perform functions of paging origination, LTE_IDLE state management,ciphering of user plane, bearer control of System Architecture Evolution(SAE), ciphering of NAS signaling and integrity protection.

FIG. 4 illustrates a radio interface protocol structure between a UE andan E-UTRAN in a wireless communication system to which the presentinvention can be applied.

FIG. 4(a) illustrates a radio protocol structure for the control plane,and FIG. 4(b) illustrates a radio protocol structure for the user plane.

With reference to FIG. 4, layers of the radio interface protocol betweenthe UE and the E-UTRAN can be divided into a first layer (L1), a secondlayer (L2), and a third layer (L3) based on the lower three layers ofthe Open System Interconnection (OSI) model, widely known in thetechnical field of communication systems. The radio interface protocolbetween the UE and the E-UTRAN consists of the physical layer, data linklayer, and network layer in the horizontal direction, while in thevertical direction, the radio interface protocol consists of the userplane, which is a protocol stack for delivery of data information, andthe control plane, which is a protocol stack for delivery of controlsignals.

The control plane acts as a path through which control messages used forthe UE and the network to manage calls are transmitted. The user planerefers to the path through which the data generated in the applicationlayer, for example, voice data, Internet packet data, and so on aretransmitted. In what follows, described will be each layer of thecontrol and the user plane of the radio protocol.

The physical layer (PHY), which is the first layer (L1), providesinformation transfer service to upper layers by using a physicalchannel. The physical layer is connected to the Medium Access Control(MAC) layer located at the upper level through a transport channelthrough which data are transmitted between the MAC layer and thephysical layer. Transport channels are classified according to how andwith which features data are transmitted through the radio interface.And data are transmitted through the physical channel between differentphysical layers and between the physical layer of a transmitter and thephysical layer of a receiver. The physical layer is modulated accordingto the Orthogonal Frequency Division Multiplexing (OFDM) scheme andemploys time and frequency as radio resources.

A few physical control channels are used in the physical layer. ThePhysical Downlink Control Channel (PDCCH) informs the UE of resourceallocation of the Paging Channel (PCH) and the Downlink Shared Channel(DL-SCH); and Hybrid Automatic Repeat reQuest (HARQ) information relatedto the Uplink Shared Channel (UL-SCH). Also, the PDCCH can carry a ULgrant used for informing the UE of resource allocation of uplinktransmission. The Physical Control Format Indicator Channel (PCFICH)informs the UE of the number of OFDM symbols used by PDCCHs and istransmitted at each subframe. The Physical HARQ Indicator Channel(PHICH) carries a HARQ ACK (ACKnowledge)/NACK (Non-ACKnowledge) signalin response to uplink transmission. The Physical Uplink Control Channel(PUCCH) carries uplink control information such as HARQ ACK/NACK withrespect to downlink transmission, scheduling request, Channel QualityIndicator (CQI), and so on. The Physical Uplink Shared Channel (PUSCH)carries the UL-SCH.

The MAC layer of the second layer (L2) provides a service to the

Radio Link Control (RLC) layer, which is an upper layer thereof, througha logical channel. Also, the MAC layer provides a function of mappingbetween a logical channel and a transport channel; andmultiplexing/demultiplexing a MAC Service Data Unit (SDU) belonging tothe logical channel to the transport block, which is provided to aphysical channel on the transport channel.

The RLC layer of the second layer (L2) supports reliable datatransmission. The function of the RLC layer includes concatenation,segmentation, reassembly of the RLC SDU, and so on. To satisfy varyingQuality of Service (QoS) requested by a Radio Bearer (RB), the RLC layerprovides three operation modes: Transparent Mode (TM), UnacknowledgedMode (UM), and Acknowledge Mode (AM). The AM RLC provides errorcorrection through Automatic Repeat reQuest (ARQ). Meanwhile, in casethe MAC layer performs the RLC function, the RLC layer can beincorporated into the MAC layer as a functional block.

The Packet Data Convergence Protocol (PDCP) layer of the second layer(L2) performs the function of delivering, header compression, cipheringof user data in the user plane, and so on. Header compression refers tothe function of reducing the size of the Internet Protocol (IP) packetheader which is relatively large and contains unnecessary control toefficiently transmit IP packets such as the IPv4 (Internet Protocolversion 4) or IPv6 (Internet Protocol version 6) packets through a radiointerface with narrow bandwidth. The function of the PDCP layer in thecontrol plane includes delivering control plane data andciphering/integrity protection.

The Radio Resource Control (RRC) layer in the lowest part of the thirdlayer (L3) is defined only in the control plane. The RRC layer performsthe role of controlling radio resources between the UE and the network.To this purpose, the UE and the network exchange RRC messages throughthe RRC layer. The RRC layer controls a logical channel, transportchannel, and physical channel with respect to configuration,re-configuration, and release of radio bearers. A radio bearer refers toa logical path that the second layer (L2) provides for data transmissionbetween the UE and the network. Configuring a radio bearer indicatesthat characteristics of a radio protocol layer and channel are definedto provide specific services; and each individual parameter andoperating methods thereof are determined. Radio bearers can be dividedinto Signaling Radio Bearers (SRBs) and Data RBs (DRBs). An SRB is usedas a path for transmitting an RRC message in the control plane, while aDRB is used as a path for transmitting user data in the user plane.

The Non-Access Stratum (NAS) layer in the upper of the RRC layerperforms the function of session management, mobility management, and soon.

A cell constituting the base station is set to one of 1.25, 2.5, 5, 10,and 20 MHz bandwidth, providing downlink or uplink transmission servicesto a plurality of UEs. Different cells can be set to differentbandwidths.

Downlink transport channels transmitting data from a network to a UEinclude a Broadcast Channel (BCH) transmitting system information, PCHtransmitting paging messages, DL-SCH transmitting user traffic orcontrol messages, and so on. Traffic or a control message of a downlinkmulti-cast or broadcast service can be transmitted through the DL-SCH orthrough a separate downlink Multicast Channel (MCH). Meanwhile, uplinktransport channels transmitting data from a UE to a network include aRandom Access Channel

(RACH) transmitting the initial control message and a Uplink SharedChannel (UL-SCH) transmitting user traffic or control messages.

Logical channels, which are located above the transport channels and aremapped to the transport channels. The logical channels may bedistinguished by control channels for delivering control areainformation and traffic channels for delivering user area information.The control channels include a Broadcast Control Channel (BCCH), aPaging Control Channel (PCCH), a Common Control Channel (CCCH), adedicated control channel (DCCH), a Multicast Control Channel (MCCH),and etc. The traffic channels include a dedicated traffic channel(DTCH), and a Multicast Traffic Channel (MTCH), etc. The PCCH is adownlink channel that delivers paging information, and is used whennetwork does not know the cell where a UE belongs. The CCCH is used by aUE that does not have RRC connection with network. The MCCH is apoint-to-multipoint downlink channel which is used for deliveringMultimedia Broadcast and Multicast Service (MBMS) control informationfrom network to UE. The DCCH is a point-to-point bi-directional channelwhich is used by a UE that has RRC connection delivering dedicatedcontrol information between UE and network. The DTCH is a point-to-pointchannel which is dedicated to a UE for delivering user information thatmay be existed in uplink and downlink. The MTCH is a point-to-multipointdownlink channel for delivering traffic data from network to UE.

In case of uplink connection between the logical channel and thetransport channel, the DCCH may be mapped to UL-SCH, the DTCH may bemapped to UL-SCH, and the CCCH may be mapped to UL-SCH. In case ofdownlink connection between the logical channel and the transportchannel, the BCCH may be mapped to BCH or DL-SCH, the PCCH may be mappedto PCH, the DCCH may be mapped to DL-SCH, the DTCH may be mapped toDL-SCH, the MCCH may be mapped to MCH, and the MTCH may be mapped toMCH.

FIG. 5 is a diagram schematically exemplifying a structure of physicalchannel in a wireless communication system to which the presentinvention can be applied.

Referring to FIG. 5, the physical channel delivers signaling and datathrough radio resources including one or more subcarriers in frequencydomain and one or more symbols in time domain.

One subframe that has a length of 1.0 ms includes a plurality ofsymbols. A specific symbol (s) of subframe (e.g., the first symbol ofsubframe) may be used for PDCCH. The PDCCH carries information forresources which are dynamically allocated (e.g., resource block,modulation and coding scheme (MCS), etc.).

Random Access Procedure

Hereinafter, a random access procedure which is provided in a LTE/LTE-Asystem will be described.

The random access procedure is performed in case that the UE performs aninitial access in a RRC idle state without any RRC connection to an eNB,or the UE performs a RRC connection re-establishment procedure, etc.

The LTE/LTE-A system provides both of the contention-based random accessprocedure that the UE randomly selects to use one preamble in a specificset and the non-contention-based random access procedure that the eNBuses the random access preamble that is allocated to a specific UE.

FIG. 6 is a diagram for describing the contention-based random accessprocedure in the wireless communication system to which the presentinvention can be applied.

(1) Message 1 (Msg 1)

First, the UE randomly selects one random access preamble (RACHpreamble) from the set of the random access preamble that is instructedthrough system information or handover command, selects and transmitsphysical RACH (PRACH) resource which is able to transmit the randomaccess preamble.

The eNB that receives the random access preamble from the UE decodes thepreamble and acquires RA-RNTI. The RA-RNTI associated with the PRACH towhich the random access preamble is transmitted is determined accordingto the time-frequency resource of the random access preamble that istransmitted by the corresponding UE.

(2) Message 2 (Msg 2)

The eNB transmits the random access response that is addressed toRA-RNTI that is acquired through the preamble on the Msg 1 to the UE.The random access response may include RA preamble index/identifier, ULgrant that informs the UL radio resource, temporary cell RNTI (TC-RNTI),and time alignment command (TAC). The TAC is the information indicatinga time synchronization value that is transmitted by the eNB in order tokeep the UL time alignment. The UE renews the UL transmission timingusing the time synchronization value. On the renewal of the timesynchronization value, the UE renews or restarts the time alignmenttimer. The UL grant includes the UL resource allocation that is used fortransmission of the scheduling message to be described later (Message 3)and the transmit power command (TPC). The TCP is used for determinationof the transmission power for the scheduled PUSCH.

The UE, after transmitting the random access preamble, tries to receivethe random access response of its own within the random access responsewindow that is instructed by the eNB with system information or handovercommand, detects the PDCCH masked with RA-RNTI that corresponds toPRACH, and receives the PDSCH that is indicated by the detected PDCCH.

The random access response information may be transmitted in a MACpacket data unit and the MAC PDU may be delivered through PDSCH.

The UE terminates monitoring of the random access response ifsuccessfully receiving the random access response having the randomaccess preamble index/identifier same as the random access preamble thatis transmitted to the eNB. Meanwhile, if the random access responsemessage has not been received until the random access response window isterminated, or if not received a valid random access response having therandom access preamble index same as the random access preamble that istransmitted to the eNB, it is considered that the receipt of randomaccess response is failed, and after that, the UE may perform theretransmission of preamble.

(3) Message 3 (Msg 3)

In case that the UE receives the random access response that iseffective with the UE itself, the UE processes the information includedin the random access response respectively. That is, the UE applies TACand stores TC-RNTI. Also, by using UL grant, the UE transmits the datastored in the buffer of UE or the data newly generated to the eNB.

In case of the initial access of UE, the RRC connection request that isdelivered through CCCH after generating in RRC layer may be transmittedwith being included in the message 3. In case of the RRC connectionreestablishment procedure, the RRC connection reestablishment requestthat is delivered through CCCH after generating in RRC layer may betransmitted with being included in the message 3. Additionally, NASaccess request message may be included.

The message 3 should include the identifier of UE. There are two wayshow to include the identifier of UE. The first method is that the UEtransmits the cell RNTI (C-RNTI) of its own through the UL transmissionsignal corresponding to the UL grant, if the UE has a valid C-RNTI thatis already allocated by the corresponding cell before the random accessprocedure. Meanwhile, if the UE has not been allocated a valid C-RNTIbefore the random access procedure, the UE transmits including uniqueidentifier of its own (for example, S-TMSI or random number). Normallythe above unique identifier is longer that C-RNTI.

If transmitting the data corresponding to the UL grant, the UE initiatesa contention resolution timer.

(4) Message 4 (Msg 4)

The eNB, in case of receiving the C-RNTI of corresponding UE through themessage 3 from the UE, transmits the message 4 to the UE by using thereceived C-RNTI. Meanwhile, in case of receiving the unique identifier(that is, S-TMSI or random number) through the message 3 from the UE,the eNB transmits the 4 message to the UE by using the TC-RNTI that isallocated from the random access response to the corresponding UE. Forexample, the 4 message may include the RRC connection setup message.

The UE waits for the instruction of eNB for collision resolution aftertransmitting the data including the identifier of its own through the ULgrant included the random access response. That is, the UE attempts thereceipt of PDCCH in order to receive a specific message. There are twoways how to receive the PDCCH. As previously mentioned, in case that themessage 3 transmitted in response to the UL grant includes C-RNTI as anidentifier of its own, the UE attempts the receipt of PDCCH using theC-RNTI of itself, and in case that the above identifier is the uniqueidentifier (that is, S-TMSI or random number), the UE tries to receivePDCCH using the TC-RNTI that is included in the random access response.After that, in the former case, if the PDCCH is received through theC-RNTI of its own before the contention resolution timer is terminated,the UE determines that the random access procedure is performed andterminates the procedure. In the latter case, if the PDCCH is receivedthrough the TC-RNTI before the contention resolution timer isterminated, the UE checks on the data that is delivered by PDSCH, whichis addressed by the PDCCH. If the content of the data includes theunique identifier of its own, the UE terminates the random accessprocedure determining that a normal procedure has been performed. The UEacquires C-RNTI through the 4 message, and after that, the UE andnetwork are to transmit and receive a UE-specific message by using theC-RNTI.

Meanwhile, the operation of the non-contention-based random accessprocedure, unlike the contention-based random access procedureillustrated in FIG. 11, is terminated with the transmission of message 1and message 2 only. However, the UE is going to be allocated a randomaccess preamble from the eNB before transmitting the random accesspreamble to the eNB as the message 1. And the UE transmits the allocatedrandom access preamble to the eNB as the message 1, and terminates therandom access procedure by receiving the random access response from theeNB.

Attach Procedure

FIG. 7 is a diagram schematically showing an attach procedure in awireless communication system to which the present invention may beapplied.

The attach procedure is used for a UE to set connection to a networkwhen entering an E-URAN cell, in general. In addition, it may be usedfor handover from a non-3GPP network to the E-UTRAN.

1-2. A UE starts the attach procedure by transmitting an Attach Requestmessage to an MME.

The Attach Request message includes international mobile subscriberidentity (IMSI) of the UE and a PDN type requested by the UE. Here, thePDN type indicates an IP version (i.e., IPv4, IPv4v6 or IPv6) requestedby the UE.

The Attach Request message is included in an RRC Connection SetupComplete message and transmitted in RRC connection and included in aninitial UE message and transmitted in S1 signaling connection.

The UE may transmit the Attach Request message along with a PDNconnectivity request in order to request PDN connectivity.

3. The MME sends a request for information for UE authentication to anHSS for UE authentication and performs mutual authentication with theUE.

4. The MME registers the location of the UE with the HSS and receivesuser subscription information (i.e., a subscribed QoS profile) from theHSS in order to generate a default bearer for the UE.

Here, subscription information does not include IP address informationabout the corresponding UE in the case of dynamic IP address allocation,whereas the subscription information includes static IP addressinformation allocated to the corresponding UE in the case of static IPaddress allocation.

5. The MME allocates a default EPS bearer ID and transmits a CreateSession Request message to an S-GW.

The Create Session Request message includes the IMSI of the UE, an EPSbearer ID, a P-GW ID (i.e., P-GW address) selected by the MME togenerate an EPS bearer, an APN, the subscribed QoS profile received fromthe HSS, the PDN type, the IP address (i.e., PDN address) of the UE,etc.

Here, the PDN type equally includes the PDN type information receivedfrom the UE. The IP address of the UE may be set to 0 in the case ofdynamic IP address allocation and set to static IP address information(included in the subscription information) allocated to thecorresponding UE in the case of static IP address allocation.

6. The S-GW allocates an S5 S-GW tunnel endpoint identifier (TEID) to aP-GW included in the Create Session Request message received from theMME in order to generate an S5 bearer and transmits the Create SessionRequest message to the P-GW.

The Create Session Request message includes the IMSI of the UE, the EPSbearer ID, an S5 S-GW TEID, the APN, the subscribed QoS profile, the PDNtype (i.e., IP version), the IP address (i.e., PDN address) of the UE,etc.

7. The P-GW allocates an Internet protocol (IP) address to be used bythe UE and performs an IP connectivity access network (IP-CAN) sessionestablishment/modification procedure with a PCRF.

Here, the P-GW may allocate an IP address selected from an IP addresspool held by the P-GW to the UE in the case of dynamic IP addressallocation, and the static IP address information (included in thesubscription information) allocated to the corresponding UE may beequally allocated in the case of static IP address allocation.

8. The P-GW allocates a P-GW TEID to the S-GW in order to generate an S5bearer and transmits a Create Session Response message to the S-GW inresponse to the Create Session Request message.

The Create Session Response message includes the IMSI of the UE, the EPSbearer ID, the S5 P-GW TEID, the subscribed QoS profile, the PDN type,the IP address (i.e., PDN address) allocated to the UE, etc.

If the P-GW selects a different PDN type from the requested PDN type,the P-GW indicates the PDN type and the cause of modification of the PDNtype to the UE.

When this procedure is finished, generation of the S5 bearer between theS-GW and the P-GW is completed and thus the S-GW may transmit uplinktraffic to the P-GW or receive downlink traffic from the P-GW.

9. The S-GW allocates an S1 S-GW TEID in order to generate an 51 bearerand transmits a Create Session Response message to the MME in responseto the Create Session Request message.

The Create Session Response message includes the IMSI of the UE, the EPSbearer ID, the 51 S-GW TEID, the PDN type, the IP address (i.e., PDNaddress) allocated to the UE, etc.

10-11. The MME transmits an Attach Accept message to the UE in responseto the Attach Request message.

The Attach Accept message includes the EPS bearer ID, the APN, the IPaddress (i.e., PDN address) of the UE allocated by the P-GW, the PDNtype, a TAI (Tracking Area Identity) list, a TAU timer, etc.

The Attach Accept message is included in an Initial Context SetupRequest and delivered to an eNB in S1 signaling connection.

When this procedure is finished, generation of an uplink S1 bearerbetween the eNB and the S-GW is completed and the eNB may transmituplink traffic to the S-GW.

In addition, the Attach Accept message is included in an RRC ConnectionReconfiguration message and delivered from the eNB to the UE in RRCconnection.

When this procedure is finished, generation of DRB between the UE andthe eNB is completed and the UE may transmit uplink traffic to the eNBor receive downlink traffic from the eNB.

12. The eNB transmits an Initial Context Setup Response message to theMME in response to the Initial Context Setup Request message. TheInitial Context Setup Response message includes an 51 eNB TEID and thelike.

13-14. The UE transmits an Attach Complete message to the MME inresponse to the Attach Accept message.

The Attach Complete message is included in a UL Information Transfermessage and transmitted in RRC connection and is included in an UplinkNAS Transport message and transmitted in 51 signaling connection.

When this procedure is finished, generation of an uplink default EPSbearer between the UE and the P-GW is completed and the UE may transmituplink data to the P-GW.

15. The MME delivers the 51 eNB TEID received from the eNB to the S-GWthrough a Modify Bearer Request message.

When this procedure is finished, generation of a downlink 51 bearerbetween the eNB and the S-GW is completed and the eNB may receivedownlink traffic from the S-GW.

16-17. The bearer between the S-GW and the P-GW is updated as necessary.

18. The S-GW transmits a Modify Bearer Response message to the MME inresponse to the Modify Bearer Request message.

When this procedure is finished, generation of a downlink default EPSbearer between the UE and the P-GW is completed and thus the P-GW maytransmit downlink data to the UE. That is, a connection between the UEand the PDN is established, and the UE may be provided with a PDNservice using the allocated IP address.

19. The MME transmits a Notify Request message including a P-GW ID(i.e., P-GW address) and APN to the HSS as necessary.

20. The HSS stores the P-GW ID (i.e., P-GW address) and associated APNand transmits a Notify Response message to the MME.

PDN Connectivity Procedure

A UE requested PDN connectivity procedure is used for a UE to requestconnection (including allocation of a default bearer) to an additionalPDN through E-UTRAN.

FIG. 8 is a diagram schematically showing a PDN connectivity procedurein a wireless communication system to which the present invention may beapplied.

1. A UE initiates a UE requested PDN procedure by transmitting a

PDN connectivity request message to an MME.

The PDN connectivity request message includes an APN, a PDN type (i.e.,IP version) requested by the UE, etc. As described above, the PDN typesindicates an IP version (i.e., IPv4, IPv4v6 or IPv6) requested by theUE.

An MME verifies whether the APN provided by the UE is permittedaccording to subscription information. If the UE does not provide theAPN to the PDN connectivity request message, the MME uses an APN from adefault PDN subscription context.

2. The MME allocates an EPS bearer ID and transmits a Create

Session Request message to an S-GW.

The Create Session Request message includes the IMSI of the UE, the EPSbearer ID, a P-GW ID (i.e., P-GW address) selected by the MME for EPSbearer generation, an APN, a subscribed QoS profile received from anHSS, a PDN type, the IP address (i.e., PDN address) of the UE, etc.

Here, the PDN type equally includes PDN type information received fromthe UE. The IP address of the UE may be set to 0 in the case of dynamicIP address allocation and may be set to static IP address information(included in subscription information) allocated to the corresponding UEin the case of static IP address allocation.

3. An S-GW allocates an S5 S-GW TEID to a P-GW included in the CreateSession Request message received from the MME in order to generate an S5bearer and transmits a Create Session Request message to the P-GW.

The Create Session Request message includes the IMSI of the UE, the EPSbearer ID, the S5 S-GW TEID, the APN, the subscribed QoS profile, thePDN type (i.e., IP version), the IP address (i.e., PDN address) of theUE, etc.

4. The P-GW allocates an IP address to be used by the UE and performs anIP-CAN session establishment/modification procedure with a PCRF.

Here, the P-GW may allocate an IP address selected from an IP addresspool held by the P-GW to the UE in the case of dynamic IP addressallocation, and the static IP address information (included in thesubscription information) allocated to the corresponding UE may beequally allocated in the case of static IP address allocation.

5. The P-GW allocates a P-GW TEID to the S-GW in order to generate an S5bearer and transmits a Create Session Response message to the S-GW inresponse to the Create Session Request message.

The Create Session Response message includes the IMSI of the UE, the EPSbearer ID, the S5 P-GW TEID, the subscribed QoS profile, the PDN type,the IP address (i.e., PDN address) allocated to the UE, etc.

If the P-GW selects a different PDN type from the requested PDN type,the P-GW indicates the PDN type and the cause of modification of the PDNtype to the UE.

When this procedure is finished, generation of the S5 bearer between theS-GW and the P-GW is completed and thus the S-GW may transmit uplinktraffic to the P-GW or receive downlink traffic from the P-GW.

6. The S-GW allocates an S1 S-GW TEID in order to generate an S1 bearerand transmits a Create Session Response message to the MME in responseto the Create Session Request message.

The Create Session Response message includes the IMSI of the UE, the EPSbearer ID, the S1 S-GW TEID, the PDN type, the IP address (i.e., PDNaddress) allocated to the UE, etc.

7. The MME transmits a PDN Connectivity Accept message to the UE inresponse to the PDN connectivity request message.

The PDN Connectivity Accept message includes the EPS bearer ID, the APN,the IP address (i.e., PDN address) of the UE allocated by the P-GW, thePDN type, etc.

The PDN Connectivity Accept message is included in a bearer setuprequest message and delivered to an eNB in S1 signaling connection.

When this procedure is finished, generation of an uplink S1 bearerbetween the eNB and the S-GW is completed and the eNB may transmituplink traffic to the S-GW.

8. The PDN Connectivity Accept message is included in an RRC connectionreconfiguration message and delivered from the eNB to the UE in RRCconnection.

When this procedure is finished, generation of DRB between the UE andthe eNB is completed and the UE may transmit uplink traffic to the eNBor receive downlink traffic from the eNB.

9. The UE transmits an RRC Connection Reconfiguration Complete messageto the eNB.

10. The eNB transmits a bearer setup response message to the MME.

The bearer setup response message includes an S1 eNB TEID and the like.

11-12. The UE transmits a PDN Connectivity Complete message includingthe EPS bearer ID to the MME.

When this procedure is finished, generation of an uplink default EPSbearer between the UE and the P-GW is completed and the UE may transmituplink data to the P-GW.

13. The MME delivers the S1 eNB TEID received from the eNB to the S-GWthrough a Modify Bearer Request message.

When this procedure is finished, generation of a downlink S1 bearerbetween the eNB and the S-GW is completed and the eNB may receivedownlink traffic from the S-GW.

13a-13b. The bearer between the S-GW and the P-GW is updated asnecessary.

14. The S-GW transmits a Modify Bearer Response message to the MME inresponse to the Modify Bearer Request message.

When this procedure is finished, generation of a downlink default EPSbearer between the UE and the P-GW is completed and thus the P-GW maytransmit downlink data to the UE. That is, connection between the UE andthe PDN is established, and the UE may be provided with a PDN serviceusing the allocated IP address.

15. The MME transmits a Notify Request message including a P-GW ID(i.e., P-GW address) and APN to the HSS as necessary.

16. The HSS stores the P-GW ID (i.e., P-GW address) and associated APNand transmits a Notify Response message to the MME.

Power Saving Mode

A power saving mode (PSM), one of 3GPP rel-12 enhancements for MTCfeatures, is a function of defining a period in which a UE disables allaccess stratum (AC) operations such as paging reception and mobilitymanagement to minimize power consumption of the UE. That is, a UEsupporting the PSM agrees on an active time and a periodic TAU (P-TAU)timer with a network or receives the same from the network during attachand tracking area update procedures.

When an active time value is received from the network, the UE maintainsan ECM-IDLE state for the corresponding active time to receive pagingupon switching from an ECM-CONNECTED state to the ECM-IDLE state. Whenthe active time expires, the UE enters the PSM and stops all ASoperations.

In addition, the MME starts the active timer with the active time valuewhenever the UE enters the ECM-IDLE mode. When the active timer expires,the MME deduces that the UE is unreachable.

That is, the active time refers to a time for which a UE that supports astate (e.g., power saving mode (PSM)) using a power saving functionmaintains an ECM-IDLE (or RRC_IDLE) state.

When the periodic TAU timer expires, the UE enables AS operations andperforms TAU and the network stops an implicit detach timer of thecorresponding UE. The UE may wake up whenever the UE wants for a mobileoriginated call (e.g., uplink data packet transfer).

On the other hand, for a mobile terminated call (e.g., downlink datapacket receiving), the UE wakes up every P-TAU period to perform TAU,performs a paging receiving operation for a received active time, andthen enters the PSM mode to sleep.

DRX (Discontinuous Reception) Mode

In the 3GPP LTE/LTE-A system, an EPS connection management(ECM)-CONNECTED state and an ECM-IDLE state are defined in order tomanage signaling connection between a UE and a network. TheECM-CONNECTED state and ECM-IDLE state may also be applied to UEs and anMME. ECM connection includes RRC connection established between a UE andan eNB and S1 signaling connection established between an eNB and anMME. RRC state indicates whether an RRC layer of a UE is logicallyconnected to an RRC layer of an eNB. That is, when the RRC layer of theUE is connected to the RRC layer of the eNB, the UE is in anRRC_CONNECTED state. When the RRC layer of the UE is not connected tothe RRC layer of the eNB, the UE is in an RRC_IDLE state.

Here, the RRC_CONNECTED state in which a UE is connected to a specificcell refers to a state in which the UE can be provided with services percell and the UE is managed per cell.

The RRC_IDLE state is a state in which a UE is not connected to an eNBand maintains only connection with a mobility management entity (MME),and the UE is managed per tracking area (TA) larger than a cell. Thatis, a UE in the RRC_IDLE state intermittently wakes up to monitor apaging channel (PCH) in order to check there is a paging messagetransmitted thereto. That is, the UE performs discontinuous reception(DRX) set by a NAS (non-access stratum) using an ID uniquely allocatedin a tracking area. The UE may receive broadcast of system informationand paging information by monitoring a paging signal at a specificpaging time per UE-specific paging DRX cycle. Further, if the identifierof the UE is included in a paging channel when the UE checks whether aterminated call is arrived, the UE switches to the RRC_CONNECTED modethrough a service request procedure. According to such network statedefinition, a UE having no activated service can minimize powerconsumption thereof and an eNB can efficiently use resources.

As described above, a UE needs to switch to an ECM connected state to beprovided with a conventional mobile communication service such as audioor data. The UE in an initial stage such as a case in which power of theUE is initially turned on is in the ECM-IDLE state, and when the UEsuccessfully registers with the corresponding network through an initialattach procedure, the UE and the MME make a transition to the ECMconnected state. Further, when the UE is registered with the network buttraffic is disabled and thus radio resources is not allocated thereto,the UE is in the ECM-IDLE state, and when new uplink or downlink trafficis generated for the UE, the UE and the MME make a transition to the ECMconnected state through a service request procedure.

The 3GPP LTE/LTE-A system uses a UE discontinuous reception (DRX)technique in order to minimize power of UEs.

DRX defined in the 3GPP LTE/LTE-A system may be used in both UE idlemode and RRC IDLE state.

A UE may perform PDCCH monitoring on the basis of an RNTI (e.g., C-RNTI,SI-RNTI, P-RNTI, etc.) which is a unique identifier of the UE.

PDCCH monitoring may be controlled by DRX operation and parameters withrespect to DRX are transmitted from an eNB to the UE through an RRCmessage. If the DRX parameters are configured in the RRC connected stateof the UE, the UE performs discontinuous monitoring for a PDCCH on thebasis of DRX operation. On the other hand, if the DRX parameters are notconfigured, the UE performs continuous PDCCH monitoring.

Furthermore, the UE which has received a paging message as describedabove may perform DRX for the purpose of reducing power consumption.

To this end, the network configures a plurality of paging occasions foreach time period called a paging cycle, and a specific UE receives apaging channel in a specific paging occasion and does not receive apaging channel in time other than the specific paging occasion. Inaddition, a single paging occasion may correspond to a single TTI.

Extended idle mode DRX (eDRX: extended DRX) is a function for minimizingUE power consumption by lengthening the conventional paging DRX cycle ofa maximum of 2.56s to several minutes to tens of minutes. eDRX may beapplied to the idle mode and the connected mode. Extended idle mode DRXapplied to the connected mode is shorter than DRX of a maximum of 10.24sapplied to the idle mode.

In the case of a UE supporting the eDRX mode, an unreachable state ofthe UE may refer to a state in which the UE is unreachable according topaging (i.e., a DRX period in which the UE does not monitor a pagingchannel).

On the contrary, in the case of a UE supporting the eDRX mode, areachable state of the UE may refer to a state in which the UE isimmediately reachable according to the ECM-CONNECTED mode and/or paging(i.e., a period in which the UE monitors a paging channel).

In other words, eDRX has a DRX period longer than that of the normal DRXmode and thus may be determined to be temporarily unreachable even in anidle period. That is, data delivery is possible after a maximum of 2.56seconds when normal DRX (2.56 seconds) is supported, whereas immediatedata delivery is impossible because maximum delay is 10 minutes, whichcan be considered to be unreachable, when eDRX (e.g., 10 minutes) isapplied.

To reduce power consumption of the UE, the UE and the network maynegotiate use of the extended idle mode DRX through NAS signaling. A UEto which the extended idle mode DRX is applied may use mobileterminating data and/or a network originated procedure within a specifictime delay depending on a DRX cycle value.

A UE (particularly, an application at the UE) which wants to use theextended idle mode DRX needs to specially control a UE terminatingservice or data delivery. Particularly, the UE needs to consider delaytolerance of UE terminating data. The network (particularly, anapplication at the network) may transmit UE terminating data, SMS or adevice trigger and needs to know whether the extended idle mode DRX isprepared. UEs should request the extended idle mode DRX only when allexpected UE terminating communications have delay tolerance.

To negotiate use of the extended idle mode DRX, the UE requests anextended idle mode DRX parameter during an attach procedure and aRAU/TAU procedure. An SGSN/MME may reject or accept the UE request forextended idle mode DRX. When the SGSN/MME accepts the extended idle modeDRX, the SGSN/MME may provide a value different from the extended idlemode DRX parameter requested by the UE on the basis of an operatorpolicy. When the SGSN/MME accepts use of extended idle mode DRX, the UEapplies extended idle mode DRX on the basis of the received extendedidle mode DRX parameter. If the SGSN/MME rejects the request or the UEcannot receive the extended idle mode DRX parameter in a relatedacknowledgement message because the request is received by an SGSN/MMEwhich do not support extended idle mode DRX, the UE applies conventionalDRX.

When the UE requests both the power saving mode (PSM) (request for anactive time and/or a periodic TAU timer) and extended idle mode DRXthrough NAS, the SGSN/MME may determine the following.

Enabling only the PSM (i.e., rejecting the request for extended idlemode DRX)

Enabling only extended idle mode DRX (i.e., rejecting the request forthe active time)

Enabling both the PSM and extended idle mode DRX (i.e., providing theactive time and the extended idle mode DRX parameter)

When one of the above three operations is determined and relatedparameters (i.e., the active time, P-TAU timer and/or extended idle modeDRX cycle value) are provided to the UE, the next attach or RAU/TAUprocedure is started and used until one of the above three operations isnewly determined. If both the extended idle mode DRX and PSM areenabled, the extended idle mode DRX cycle may be set to have a pluralityof paging occasions while an active timer operates.

When a PSM active time provided by the UE is longer than the extendedidle mode DRX cycle, the SGSN/MME may enable both the PSM and extendedidle mode DRX. This may minimize power consumption of the UE during theactive time.

Machine-Type Communication (MTC)

FIG. 9 is a diagram showing an architecture for machine-typecommunication (MTC) in a wireless communication system to which thepresent invention is applicable.

An end-to-end application between a UE used for MTC (or MTC UE) and anMTC application may use services provided by a 3GPP system and optionalservices provided to an MTC server. The 3GPP system may providetransport and communication services (including a 3GPP bearer service,IMS and SMS) including various types of optimization for facilitatingMTC.

FIG. 9 shows connection of a UE used for MTC to a 3GPP network (UTRAN,E-UTRAN, GERAN, I-WLAN, etc.) through an Um/Uu/LTE-Uu interface. Thearchitecture of FIG. 9 includes various MTC models (a direct model, anindirect model and a hybrid model).

First, entities shown in FIG. 9 will be described.

In FIG. 9, an application server is a server on a network in which anMTC application is executed. The above-described various technologiesfor realizing the MTC application can be applied to the MTC applicationserver and detailed description thereof is omitted. In addition, the MTCapplication server in FIG. 9 may access an MTC server through areference point API. Detailed description thereof is omitted.Alternatively, the MTC application server may be collocated with the MTCserver.

The MTC server (e.g., SCS server in FIG. 9) is a server on a networkwhich manages MTC UEs and may be connected to a 3GPP network tocommunicate with UEs used for MTC and PLMN nodes.

An MTC-interworking function (MTC-IWF) may administer interworkingbetween the MTC server and an operator core network and may serve as aproxy of MTC operation. To support the MTC indirect or hybrid model, theMTC-IWF may relay or interpret a signaling protocol on a reference pointTsp to cause a PLMN to operate a specific function. The MTC-IWF mayexecute a function of authenticating the MTC server before the MTCserver establishes communication with the 3GPP network, a function ofauthenticating a control plane request from the MTC server, variousfunctions associated with trigger indication which will be describedlater, etc.

A short message service-service center (SMS-SC)/Internet protocol shortmessage gateway (IP-SM-GW) may manage transmission and reception ofshort message service (SMS). The SMS-SC may relay, store and delivershort messages between a short message entity (SME) (entity transmittingor receiving short messages) and UEs. The IP-SM-GW may manage protocolinterworking between IP based UEs and the SMS-SC.

A charging data function (CDF)/charging gateway function (CGF) mayperform charging related operations.

An HLR/HSS may execute functions of storing subscriber information (IMSIand the like), routing information, configuration information, etc. andproviding the information to the MTC-IWF.

An MSC/SGSN/MME may execute control functions such as mobilitymanagement, authentication and resource allocation for connection of UEsto a network. This may execute a function of receiving triggerindication from the MTC-IWF with respect to triggering which will bedescribed later and processing the trigger indication into a message tobe provided to MTC UEs.

A gateway GPRS support node (GGSN)/serving-gateway (S-GW)+packet datenetwork-gateway (P-GW) may serve as a gateway which manages connectionbetween a core network and an external network.

Table 2 shows major reference points in FIG. 9.

TABLE 2 Reference point Description Tsms Reference point used for anexternal entity of a 3GPP system to communicate with an MTC UE throughSMS Tsp Reference point used for an external entity of a 3GPP system tocommunicate with the MTC-IWF with respect to control plane signaling T4Reference point used by the MTC-IWF to route device trigger to an SMS-SCof an HPLMN T5a Reference point between the MTC-IWF and a serving SGSNT5b Reference point between the MTC-IWF and a serving MME T5c Referencepoint between the MTC-IWF and a serving MSC S6m Reference point used bythe MTC-IWF to inquire about UE identification information (E.164 MobileStation International Subscriber Directory Number (MSISDN), IMSI mappedto an external identifier, or the like) and collect UE reachability andconfiguration information

In Table 2, one or more of the reference points T5a, T5b and T5c arereferred to as T5.

Meantime, user plane communication with the MTC server in the case ofthe indirect and hybrid models and communication with the MTCapplication server in the case of the direct and hybrid models may beperformed using a conventional protocol through reference points Gi andSGi.

Details related to the description of FIG. 9 may be incorporated byreference by referring to 3GPP TS 23.682 document.

FIG. 10 shows an architecture for service capability exposure in awireless communication system to which the present invention isapplicable.

The architecture for service capability exposure shown in FIG. 10enables a 3GPP network to safely expose service and capability thereofprovided by a 3GPP network interface to an external third party serviceprovider.

A service capability exposure function (SCEF) is a core entity in a 3GPParchitecture for service capability exposure which provides a means forsafely exposing service and capability provided by the 3GPP networkinterface. In other words, the SCEF is a core entity for providing aservice function, which belongs to the trust domain operated by a mobilecarrier. The SCEF provides an API interface to a third party serviceprovider and provides 3GPP service functions to the third party serviceprovider through connection with various entities of 3GPP. The SCEF maybe provided by an SCS.

When Tsp function can be exposed through an application programinterface (API), the MTC-IWF may be collocated with the SCEF. A protocol(e.g., DIAMETER, RESTful APIs, XML over HTTP, etc.) for specifying a new3GPP interface depending on multiple factors is selected. Here, themultiple factors include easiness of exposure of requested informationor necessity for a specific interface but are not limited thereto.

The SCEF is an entity belonging to a trust domain and may be operated bya cellular operator or a trusted third party service provider. This is anode for exposing service architecture proceeding under a work item suchas monitoring enhancement (MONTE), architecture enhancements for servicecapability exposure (AESE) of 3GPP Release 13 and performs managementsuch as providing functions related to monitoring and charging to anexternal third party by being connected to 3GPP entities which willprovide services as shown in FIG. 10 and configuring a communicationpattern of a third party service provider in an EPS.

Efficient Small Data Transmission for Narrow Band Internet of Things(IOT)

Cellular Internet of Things (CIoT) is a definition of new wirelessaccess suitable for IoT service, and two CIoT schemes are underdiscussion in 3GPP Release-12. One is a solution evolving from GERANinto CIoT and the other is a new wireless access network form suitablefor narrow band (NB) radio access technology (RAT) called “clean slate”.

An architecture with respect to a new core network for efficient smalldata transmission for supporting narrow band IoT is under discussion in3GPP.

FIG. 11 is a diagram showing an end-to-end small data flow in a wirelesscommunication system to which the present invention is applicable.

As shown in FIG. 11, non-IP data may be transmitted and received betweenan AS and a CIoT serving gateway node (C-SGN) through a point-to-pointtunnel. The C-SGN is a node added to Rel-13 in order to support CIoTUEs.

Further, an SCEF framework may be used to transmit/receive non-IPpackets. In other words, non-IP data may be transmitted and receivedbetween an AS/SCS and the C-SGN through the SCEF.

In addition, non-IP data may be transmitted and received between theC-SGN and a UE through an S1-MME reference point. That is, encryptedsmall data (e.g., non-IP data) may be transmitted and received betweenthe UE and the C-SGN in the NAS.

The C-SGN is a new logical entity and may be realized to support onlyessential functions required for the following CIoT use cases.

Some procedures required in a mobility management (MM) procedure

Efficient small data procedure

Security procedure required for efficient small data.

SMS on PS domain using a non-combined GPRS attach procedure when shortmessage service (SMS) support is required

Paging optimization for coverage enhancement

Termination of SGi interface for non-roaming cases

S8 interface support for roaming cases

Supporting attach (i.e., attach for only for SMS transmission andreception without PDN connectivity for IP (or non-IP)) procedure foronly SMS

Supporting tunneling on SGi for non-IP data

In addition, the following solution for small data (e.g., non-IP data)transmission using the SCEF is under discussion.

Solution) Non-IP small data transmission through the SCEF whichminimizes a load applied to HSS

FIG. 12 shows a cellular IoT network architecture proposed for efficientnon-IP small data transmission through the SCEF in a wirelesscommunication system to which the present invention is applicable.

T6a is a reference point used between the SCEF and a serving MME and T6bis a reference point used between the SCEF and a serving SGSN. T6a/T6bsatisfy the following requirements.

T6a connects the SCEF to the serving MME.

T6b connects the SCEF to the serving SGSN.

Functions such as configuring a monitoring event in the serving MME/SGSNby the SCEF and reporting a monitoring event to the SCEF by the servingMME/SGSN are supported.

Non-IP data delivery (NIDD) from the serving MME/SGSN

S6t is a reference point used between the SCEF and an HSS and satisfiesthe following requirements.

The SCEF is connected to the HSS including subscription and UE relatedinformation.

Monitoring event configuration/deletion in the HSS by SCEF

Monitoring event report to the SCEF by the HSS

Configuration/deletion of communication pattern parameters by the SCEFfor the HSS

First, a monitoring event configuration procedure will be described.

A monitoring event of small data transmission (SDT) may be configured asfollows.

Prior to mobile originated (M)) and mobile terminated (MT) small datatransmission, the MME/C-SGN and the SCEF acquire information (SCEF IDand MME/C-SGN routing information) necessary for MO and MT small datatransmission through a monitoring event configuration procedure.

FIG. 13 shows a monitoring event configuration and deletion procedurethrough the HSS in a wireless communication system to which the presentinvention is applicable.

1. An SCS/AS transmits a monitoring request message (externalidentifier(s)) or mobile station integrated system digital networks(MSISDN), an SCS/AS identifier, an SCS/AS reference ID, a monitoringtype, a maximum number of reports, a monitoring duration, a monitoringdestination address and an SCS/AS reference ID for deletion) to theSCEF.

Here, the SCS/AS may set the monitoring type to “SDT”.

2. The SCEF stores the SCS/AS reference ID, SCS/AS identifier,monitoring destination address, monitoring duration and maximum numberof reports. The SCEF allocates the SCEF reference ID. If the SCS/AS isnot authorized to perform this request, the monitoring request ismalformed or the SCS/AS exceeds a quota or rate of monitoring requestsubmission on the basis of an operator policy, the SCEF performs step 9and provides an appropriate cause value indicating an error. If the SCEFreceives the SCS/AS reference ID for deletion, the SCEF derives arelated SCEF reference ID for deletion.

3. The SCEF transmits a monitoring request message (an externalidentifier or MSISDN, an SCEF ID, an SCEF reference ID, a monitoringtype, a maximum number of reports, a monitoring duration, SCEF referenceID for deletion, and a chargeable party identifier) to the HSS in orderto configure a given monitoring event in the HSS and MME/SGSN.

4. The HSS checks the monitoring request message. For example, the HSSchecks whether the parameters included in the message are in a rangeacceptable by the operator with respect to the presence of the externalidentifier or MSISDN, whether monitoring events are supported by theserving MME/SGSN or whether a monitoring event to be deleted is valid.The HSS optionally authorizes a chargeable party identified by thechargeable party identifier. If the aforementioned checking fails, theHSS conforms to step 8 and provides a cause value indicating the causeof the failure state to the SCEF.

The HSS stores the SCEF reference ID, the SCEF ID, the maximum number ofreports, the monitoring duration and the SCEF reference ID for deletionprovided by the SCEF.

5. When a specific monitoring type is requested and the monitoringevents are supported by the serving MME/SGSN, the HSS transmits anInsert Subscriber Data Request message (the monitoring type, the SCEFID, the SCEF reference ID, the maximum number of reports, the monitoringduration, the SCEF reference ID for deletion and the chargeable partyidentifier) to the MME/SGSN.

6. The MME/SGSN verifies the request. For example, if the monitoringtype is covered according to roaming agreement when the request istransmitted from another PLMN, whether the SCEF reference ID fordeletion can be served and deleted is checked. When this check fails,the MME/SGSN conforms to step 7 and provides a cause value indicatingthe cause of the failure state to the SCEF. The MME/SGSN may reject therequest for another cause (e.g., overload or whether the HSS exceeds themonitoring request submission quota or rate) on the basis of theoperator policy.

The MME/SGSN stores received parameters and, when the request is aone-time request and a monitoring event is not available in the MME/SGSNon an Insert Subscriber Data Answer transmission occasion, starts tomonitor the indicated monitoring event. The MME/SGSN deletes amonitoring configuration identified by the SCEF reference ID fordeletion.

7. When the monitoring configuration has been successfully performed,the MME/SGSN transmits an Insert Subscriber Data Answer (cause) messageto the HSS. If the requested monitoring event is available in theMME/SGSN on the Insert Subscriber Data Answer transmission occasion, theMME/SGSN includes a monitoring event report in the Insert SubscriberData Answer message.

8. The HSS transmits a monitoring response message (the SCEF referenceID and cause) to the SCEF in order to acknowledge authentication of themonitoring request and deletion of the identified monitoring eventconfiguration. The HSS deletes the monitoring event configurationidentified by the SCEF reference ID. If the requested monitoring eventis available for the HSS on the monitoring response message transmissionoccasion or the requested monitoring event is received from the MME/SGSNin step 7, the HSS includes a monitoring event report in the monitoringresponse message.

If the request is a one-time request and Insert Subscriber Data Answerincludes the monitoring event report, the HSS deletes the relatedmonitoring event configuration.

In the case of UE mobility, the HSS determines whether a new MME/SGSNsupports the requested monitoring event.

Here, if the monitoring type received in step 3 is set to “SDT”, the HSSmay include routing information of the MME/C-SGN in the monitoringresponse message.

9. The SCEF transmits the monitoring response message (the SCS/ASreference ID and cause) to the SCS/AS in order to acknowledgeauthentication of the monitoring request and deletion of the identifiedmonitoring event configuration. If the SCEF receives the monitoringevent report, the SCEF includes the monitoring event report in themonitoring response message. If the request is a one-time request andthe monitoring response includes the monitoring event report, the SCEFdeletes the related monitoring event configuration.

Common parameters related to the monitoring event configurationprocedure shown in FIG. 13 are as follows.

The SCS/AS reference ID is a parameter generated by the SCS/AS andindicates specific transaction initiated by the SCS/AS for the SCEF. TheSCS/AS reference ID is stored in the SCEF.

The SCEF reference ID is generated by the SCEF to correlate a monitoringevent report or monitoring event deletion with a specific monitoringrequest and related context information in the SCEF. The SCEF referenceID is stored in the HSS, the MME or the SGSN.

The SCEF ID indicates the SCEF to which a monitoring indication messageneeds to be transmitted by the HSS, the MME or the SGSN. The SCEF ID isstored in the HSS, the MME or the SGSN.

The monitoring type identifies a requested specific monitoring event.

The maximum number of reports is an optional parameter and indicates amaximum number of event reports generated by the HSS, the MME or theSGSN until an associated monitoring event is considered to expire.

The monitoring duration is an optional parameter and indicates anabsolute time when an associated monitoring event request is consideredto expire.

Inclusion of the maximum number of repeats (having a value greaterthan 1) or the monitoring duration indicates that a monitoring requestis continuous monitoring requests. In continuous monitoring requests, asingle monitoring request may generate a plurality of monitoringindication messages.

Non-existence of the maximum number of reports and the monitoringduration indicates that a monitoring request is a one-time monitoringrequest. In one-time monitoring requests, a single monitoring requestgenerates a single monitoring report.

When both the maximum number of reports and the monitoring duration areincluded in a given monitoring event, a monitoring request is consideredto expire when a single condition is satisfied.

The monitoring destination address is an optional parameter included bythe SCS/AS in order to indicate delivery of monitoring indications to adifferent address from a requested SCS/AS address. Non-existence of thisparameter indicates that monitoring indications are delivered to theSCS/AS in which a monitoring request is generated.

The SCS/AS reference ID for deletion identifies a monitoring eventconfiguration which needs to be deleted before a requested monitoringevent configuration is applied.

The SCEF reference ID for deletion identifies a monitoring eventconfiguration which needs to be deleted before a requested monitoringevent configuration is applied.

The chargeable party identifier is an optional parameter included by theSCEF. This parameter identifies an entity for which accounting/chargingfunctions are executed by an associated 3GPP network element.

Hereinafter, an MO small data (i.e., IP, non-IP, SMS) transmissionprocedure will be described.

FIG. 14 shows an MO small data transmission procedure in a wirelesscommunication system to which the present invention is applicable.

1a. A monitoring event is detected by a node (i.e., MME/C-SGN) for whichthe monitoring event is configured.

That is, the MME/C-SGN may detect the monitoring event by receiving MOsmall data.

More specifically, a UE may send a request for establishment of RRCconnection to the AS of the UE. A new NAS message format which carriessmall data packets in an encrypted information element (IE) may be used.Here, unencrypted part of this new NAS PDU may carry “eKSI and sequencenumber” IE. The MME/C-SGN may use “eKSI and sequence number” IE andSAE-temporary mobile subscriber identity (S-TMSI) to identify a securitycontext for decrypting small data packets. A RAN may deliver a NAS PDUto the MME/C-SGN. The MME/C-SGN may decrypt a NAS message and obtainsmall data packets.

2a. The node (i.e., MME/C-SGN) transmits a monitoring indication message(an SCEF reference ID and a monitoring event report) to the SCEF. If amonitoring event configuration is triggered by a one-time monitoringrequest, the monitoring event configuration is deleted by the MME/SGSNwhen this step is finished. If the MME/SGSN has a maximum number ofreports stored for this monitoring task, the MME/SGSN decreases thevalue by 1.

Here, the monitoring event report may include MO small data. The SCEFmay respond to the MME/C-SGN using an acknowledgement message.

3. The SCEF retrieves a related SCS/AS reference ID along with amonitoring destination address or an SCS/AS address as a destination towhich the monitoring indication message will be transmitted using theSCEF reference ID. The SCEF transmits the monitoring indication message(SCS/AS reference ID, external ID or MSISDN and monitoring information)to the identified destination.

When the maximum number of reports is reached for a continuousmonitoring request, the SCEF sends a request for deletion of the relatedmonitoring event configuration and the associated monitoring eventconfiguration according to steps 3 to 8 of the procedure of FIG. 13 toan HSS (in the case of a monitoring event configured through the HSS) orMME(s)/SGSN(s) (in the case of a monitoring event directly configured inthe MME/SGSN).

When a report about a one-time monitoring request set through the HSS isreceived from the MME/SGSN (step 2a), the SCEF sends a request fordeletion of the related monitoring event configuration and theassociated monitoring event configuration according to steps 3 to 8 ofthe procedure of FIG. 13 to the HSS.

Here, the SCEF may transmit MO small data to a monitoring destinationnode through a monitoring report procedure.

Hereinafter, an MT small data (i.e., IP data, non-IP data and SMS)transmission procedure will be described.

FIG. 15 shows an MT small data transmission procedure in a wirelesscommunication system to which the present invention is applicable.

1. An SCS/AS transmits a small data transmission (SDT) request message(an SCS/AS reference ID for SDT and MT small data) to the SCEF.

2. If the SCEF does not have routing information which is valid for anMME/C-SGSN corresponding to the SCS/AS reference ID for SDT, the SCEFqueries an HSS.

3. The SCEF transmits the SDT request message (SCS/AS reference ID forSDT, and MT small data) to the MME/C-SGN.

The MME/C-SGN may transmit the MT small data to a UE.

More specifically, the MME/C-SGN may receive small data packets from theSCEF. If there is no signaling connection to the UE, the MME/C-SGN maybuffer the received small data packets and transmit paging to the UE.The UE may transmit a service request message to the MME/C-SGN as aresponse to the paging. Then, the C-SGN may transmit the small datapackets in an encrypted IE in a NAS PDU in a downlink NAS message, andan RAN may transmit the NAS PDU to the UE.

4. The MME/C-SGN transmits an SDT response message (an SCEF reference IDfor SDT, and cause) to the SCEF.

If a valid context related to the SCEF reference ID for SDT is notpresent in the MME/C-SGN, the MME/C-SGN notifies the SCEF of MT smalldata transmission failure by setting the cause to an appropriate value.In this case, the SCEF may perform the procedure from step 2 again.

5. The SCEF transmits the SDT response message (SCS/AS reference ID forSDT, and cause) to the SCS/AS.

Non-IP Data Delivery (NIDD)

Functions for NIDD may be used for UEs to process mobile originated (MO)and mobile terminated (MT) communication. Here, packets used forcommunication may be regarded as unstructurized from an ESP standpoint.That is, these packets may be called non-Internet protocol (non-IP)packets (or data). That is, a non-IP packet may refer to a packet whichdoes not include a source IP address and a destination IP address in theheader thereof and may be understood as the same concept as small datain the present description. Support of non-IP data is part of CIoT EPSoptimization. Non-IP data delivery to an SCS/AS may be performed usingone of the following two mechanisms.

Delivery Using the SCEF

Delivery using a point-to-point (PtP) SGi tunnel

NIDD via the SCEF is processed using PDN connection to the SCEF. A UEmay acquire non-IP PDN connection to the SCEF during an attach procedureor UE requested PDN connectivity or PDP context activation procedure.

The UE cannot recognize whether non-IP PDN connection is provided viathe SCEF or a PGW.

Association between the SCS/AS and the SCEF needs to be established suchthat non-IP data delivery can be performed between the UE and theSCS/AS.

NIDD via the SCEF uses user identity in order to identify a UE to whichspecific T6a/T6b connection belongs. User identity is one of user IMSI,MSISDN and an external identifier. The user IMSI is not used for aninterface between the SCEF and the SCS/AS.

To perform NIDD or transmit or receive NIDD data, the SCS/AS uses theMSISDN or the external identifier to identify the user. To enablecorrelation of the SCS/AS which requests T6a/T6b for a given UE, the HSSprovides the user IMSI to the SCEF and, if possible, provides the MSISDN(when an NIDD configuration request includes the external identifier) orthe external identifier (when the NIDD configuration request includesthe MSISDN).

The SCEF may buffer MO and/or MT non-IP data according to operatorpolicy.

Protocol configuration options (PCO) may be used to deliver parameters(e.g., a maximum packet size and the like) between the UE and the SCEF.Information of the PCO may be transparently delivered through theMME/SGSN. The PCO is transmitted in EPS session management signalingbetween the UE and the MME and transmitted in GPRS session managementsignaling between the UE and the SGSN.

Hereinafter, a link setup process for UL/DL data (i.e., non-IP data)transmission through the MME/SGSN and SCEF will be described.

FIG. 16 shows a link setup process for UL/DL data (i.e., non-IP data)transmission through the MME and SCEF in a wireless communication systemto which the present invention is applicable.

Since an IP protocol is not used for transmission and reception ofnon-IP data, the data may be transmitted and received using a P2Pmethod. To apply this method to networks, a link (i.e., PDN connectionfor non-IP data transmission and reception) may be set up in advancebetween a UE and a PDN (i.e., an access point name (APN)) via the MMEand the SCEF.

Here, the APN refers to a PDN identifier (i.e., PDN ID) and represents acharacter string for indicating or identifying the PDN. A P-GW thatneeds to be used by the UE may be determined using the APN. Further, atunnel through which the UE is connected to the PDN may be defined usingthe APN. Each PDN may have an APN for identifying the corresponding PDNand one or more P-GWs associated with the corresponding PDN.

1) First, an NIDD configuration procedure is performed.

Connection setup between SCS/AS and the SCEF may be referred to as NIDDconfiguration. This may be regarded as prior to T6a connection setup.That is, the NIDD configuration procedure may be performed before athird party service provider contracts with an operator for IoT businessand IoT UEs are deployed and registered with the network.

The SCS/AS requests setup from the SCEF for a UE which wants connectionsetup using the MSISDN or external identity of the UE. Then, the SCEFrequests authentication handling of the UE and the SCS/AC and UE IDresolution from the HSS. That is, IMSI is a UE identifier that cannot beexposed to an external network (i.e., SCS/AS), and thus the externalnetwork can identify the UE using an MSISDN (i.e. UE number) or anexternal identifier, in general, as described above. Information onmapping between ID and IMSI is stored in the HSS. When the NIDDconfiguration procedure is successfully completed, NIDD configuration iscompleted and a context with respect to the corresponding UE isgenerated in the SCEF.

Here, the NIDD configuration procedure is performed through an APIinterface.

The NIDD configuration procedure will be described in more detail withreference to FIG. 17.

2a) The UE transmits a PDN connection request message to the MME.

The UE transmits APN information along with a non-IP type indication tothe MME while requesting PDN connection setup (i.e., transmitting thePDN connection request message). Then, the MME checks subscriptioninformation corresponding to the APN through the HSS and determineswhether PDN connection setup using the SCEF is performed.

2b) A T6a connection establishment procedure is performed.

If invoke SCEF selection is enabled as shown in Table 3, the MME startssetup of T6a connection to the SCEF. A destination SCEF used in thiscase may also use subscription information of the UE, which is stored inthe HSS.

As described above, the UE requests PDN connection from the MME when theUE wants attachment or services. The MME determines whether T6aconnection is established with reference to the subscription informationof the UE when requested PDN connection is non-IP type (i.e., PDN typeis “non-IP”).

The T6a connection establishment procedure will be described in moredetail with reference to FIG. 18.

Table 3 shows information stored in the HSS for SCEF connection.

TABLE 3 Field Example PDN address) N/A PDN type Non-IP Access point namewww.3rdparty-service.com (APN) Invoke SCEF selection Yes SCEF IDxxx.xxx.xxx

FIG. 17 shows an NIDD configuration procedure in a wirelesscommunication system to which the present invention is applicable.

1. The SCS/AS transmits an NIDD configuration request message (externalidentifier or MSISDN, SCS/AS identifier, SCS/AS Reference ID, NIDDduration, NIDD destination address and SCS/AS reference ID for deletion)to the SCEF.

2. The SCEF stores the external identifier or MSISDN, SCS/AS referenceID, SCS/AS identifier, NIDD destination address and NIDD duration. Whenthe SCS/AS is not authorized to perform this request or the NIDDconfiguration request is malformed, the SCEF performs step 6 andprovides a cause value indicating an error. The SCEF may change the NIDDduration according to configuration.

3. The SCEF transmits an NIDD authorization request message (externalIdentifier or MSISDN and APN) to the HSS in order to authorize the NIDDconfiguration request with respect to the received external identifieror MSISDN and to receive information necessary for NIDD.

4. The HSS checks the NIDD authorization request message (with respectto existence of the external identifier or MSISDN or mapping between theexternal identifier and IMSI and/or MSISDN). When checking fails, theHSS conforms to step 5 and provides a result indicating the cause of thefailure state to the SCEF.

5. The HSS transmits an NIDD authorization response message (IMSI,MSISDN or external identifier, and result) to the SCEF in order toacknowledge authentication of the NIDD authorization request. The IMSI,and if possible, the MSISDN (when the NIDD configuration requestincludes the external identifier) or external identifier(s) (when theNIDD configuration request includes the MSISDN) are returned by the HSSin this message. This authorizes the SCEF to correlate T6a/T6bconnection (refer to FIG. 18 below) established for the correspondinguser with the SCS/AS request received in step 1 of this procedure.

6. The SCEF transmits an NIDD configuration response message (SCS/ASreference ID and cause) to the SCS/AS in order to acknowledgeauthentication of the NIDD configuration request and deletion of theidentified NIDD configuration.

FIG. 18 shows a T6a connection establishment procedure in a wirelesscommunication system to which the present invention is applicable.

When a UE performs an EPS attach procedure involving a PDN type of“non-IP” (refer to FIG. 7) and subscription information corresponding toa default APN for the PDN type of “non-IP” or an APN requested by the UEincludes an “Invoke SCEF Selection” indicator, the MME starts T6a/T6bconnection to the SCEF corresponding to an “SCEF ID” indicator for thecorresponding APN.

1. The UE performs steps 1 to 11 of the UTRAN initial attach procedure(refer to 7) or step 1 of the UE requested PDN connectivity procedure(refer to FIG. 8).

The MME receives subscription information and SCEF ID for non-IP PDNconnection to the APN correlated with the “Invoke SCEF Selection”indicator.

If MSISDN is correlated with subscription of the user, MSISDN isprovided by the HSS to the MME as user identity.

2. When the subscription information corresponding to the default APNfor “non-IP” PDN type or the UE requested APN includes the “Invoke SCEFSelection” indicator, the MME generates PDN connection to the SCEF andallocates EPS bearer identity to the PDN connection, instead of steps 12to 16 of the UTRAN initial attach procedure (refer to FIG. 7) or steps 2to 6 of the UE requested PDN connectivity procedure (refer to FIG. 8).Here, an EPS bearer is a transmission path of traffic generated betweena UE and a PDN GW in order to deliver user traffic in the EPS, and EBIis an identifier for identifying the EPS bearer.

This is performed by transmitting, by the MME, a Create SCEF ConnectionRequest message (user identity, EBI, SCEF ID, APN and APN Rate Control,Serving PLMN Rate Control, number of PDN connections and PCO) to theSCEF.

When an IWK-SCEF (here, the IWK-SCEF corresponds to a node used duringroaming) receives the Create SCEF Connection Request message from theMME, the IWK-SCEF delivers the message to the SCEF.

The SCEF may uniquely identify PDN connection thereto for the given UEby combining the EBI, APN and user identity.

If the SCS/AS and the SCEF perform the NICC configuration procedure forthe user identity received in step 2, step 3 is performed. If the SCS/ASdoes not perform the NIDD configuration procedure for the user identityreceived in step 2, the SCEF rejects T6a connection setup or starts anNIDD configuration procedure set in the SCEF along with the SCEF usingimplementation of a specific procedure.

If NIDD is not configured, T6a connection instead of end-to-endconnection may be rejected even if T6a connection is established or NIDDconfiguration may be triggered according to implementation.

3. The SCEF generates a SCEF EPS bearer context for the UE identifiedthrough the user identity and EBI. The SCEF transmits a Create SCEFConnection Response message (user identity, EBI, SCEF ID, APN, PCO andNIDD charging ID) for confirming establishment of PDN connection to theSCEF for the UE to the MME.

When the IWK-SCEF receives the Create SCEF Connection Response messagefrom the SCEF, the IWK-SCEF delivers the message to the MME.

Upon completion of the procedures of FIGS. 17 and 18, a context isgenerated in the SCEF for the corresponding UE and non-IP PDN connectionthrough the SCEF is generated.

Next, a downlink PDN connected data transmission procedure through theSCEF.

FIG. 19 shows a mobile terminated NIDD procedure in a wirelesscommunication system to which the present invention is applicable.

FIG. 19 shows a procedure used for an SCS/AS to transmit non-IP data toa user identified through an external identifier or MSISDN. Thisprocedure is based on the assumption that the procedure of FIG. 18 iscompleted.

1. When NIDD service has been enabled for a given UE and the SCS/AS hasnon-IP data to be transmitted to the UE, the SCS/AS transmits an NIDDSubmit Request message (an external identifier or MSISDN, an SCS/ASreference ID and non-IP data) to the SCEF.

Here, the SCS/AS reference ID corresponds to a value provided by theSCS/AC when NIDD is configured and is also received when an NIDDconfiguration response is received from the SCEF. In addition, theSCS/AS use the SCS/AS reference ID for data transmission.

2. When an SCEF EPS bearer context corresponding to the externalidentifier or MSISDN included in step 1 is discovered, the SCEF checkswhether the SCS/AS has been authorized to transmit an NIDD request andwhether the SCS has not exceeded the quota (e.g., 200 bytes within 24hours) or rate (e.g., 10 bytes per hour) of data submission thereof.

When this check fails, the SCEF transmits an NIDD response including acause value indicating the cause of the failure state and stops theoperation in this step. Otherwise, the procedure proceeds to step 3.

When the SCEF EPS bearer context is not discovered, the SCEF may performany one of the following operations according to configuration.

An operation of transmitting an NIDD response including an appropriateerror cause value and stopping the operation in this step.

An operation of performing device triggering for the UE in order toestablish non-IP PDN connection to the SCEF. In this case, step 6 isperformed with an appropriate cause value.

An operation of accepting the NIDD Submit Request is accepted,performing step 6 with an appropriate cause value, and waiting for theUE to perform a procedure of causing establishment of PDN connection tothe SCEF.

3. When the SCEF EPS bearer context corresponding to the externalidentifier or MSISDN included in step 1 is discovered, the SCEFtransmits an NIDD Submit Request message (user identity, an EBI, an SCEFID and non-IP data) to an MME.

When an IWK-SCEF receives the NIDD Submit Request message from the SCEF,the IWK-SCEF relays the message to the MME.

4. When the MME can immediately deliver the non-IP data to the UE (e.g.,the UE is in an ECM_CONNECTED mode or the UE is in an ECM_IDLE mode andthe MME can state a paging procedure), a non-IP data delivery procedureis performed in step 8.

If the MME knows that the UE is unreachable when the UE uses a powersaving function (e.g., PSM mode or eDRX), the MME transmits an NIDDSubmit Response message (causes and reachable for NIDD) to the SCEF. Thecause parameter indicates that the non-IP data has not been delivered tothe UE. The reachable for NIDD flag indicates that the MME will notifythe SCEF that the UE is reachable when the MME determines that the UE isreachable. The MME stores the reachable for NIDD flag in an EMM contextfor the UE.

5. The SCEF may transmit an NIDD response to the SCS/AS which notifiesthe SCEF of the result received from the MME. When the SCEF receives thereachable for NIDD flag from the MME, the SCEF may buffer the non-IPdata requested in step 3 on the basis of configuration.

6. When the MME detects that the UE is reachable (e.g., when the UEexits a PSM mode by performing TAU or starts MO communication), the UEbecomes reachable (e.g., an eDRX cycle expires, an MO communicationpattern of the UE predicted by the MME, etc.), and the MME can reach anNIDD flag set, the MME transmits an NIDD Submit Indication message (useridentity) to the SCEF. The MME clears the reachable for NIDD flag fromthe EMM context.

7. The SCEF transmits the NIDD Submit Request message (user identity,EBI, SCEF ID and non-IP data) to the MME.

8. If required, the MME pages the UE and delivers the non-IP data to theUE using a data delivery procedure through the MME.

9. When the MME can start step 8, the MME transmits an NIDD SubmitResponse Cause message to the SCEF as acknowledgement for the NIDDSubmit Request message received from the SCEF in step 3 or 7. The SCEFconfirms non-IP data delivery to the SCS/AS.

Serving Node Relocating Method

The present invention proposes a method of processing change (orrelocation) of a serving node (e.g., MME/SGSN or C-SGN) in theabove-described method (refer to FIGS. 14 and 15) of transmitting non-IPsmall data (i.e., small data or non-IP data) via the SCEF.

In the present description, small data may be interpreted as non-IPdata.

For example, when non-IP data is transmitted as shown in FIG. 15, if aserving node (e.g., MME/SGSN or C-SGN) is changed due to UE handover andthe SCEF transmits non-IP data to the serving node because the SCEF doesnot recognize the UE handover (step 3 in FIG. 15), a previous MMEtransmits a response message including a cause value indicating an errorto the SCEF. Accordingly, the SCEF may perform an inefficient operationof inquiring an HSS about the location of the serving node (i.e.,routing information) and then transmitting the non-IP data to a newserving node.

Therefore, the present invention proposes a method by which the SCEF canbe aware of correct information of the serving node in this case.

In addition, the present invention proposes a method by which an SCS/ASsuccessfully transmits non-IP data to a UE even when a serving node ofthe UE changes when a UE reachability monitoring event is used.

Particularly, the present invention proposes a method by which the SCEFrecognizes the serving node (e.g., MME/SGSN or C-SGN) of the UE suchthat the SCEF can transmit data to the serving node without querying tothe HSS about the information of the serving node every time when theSCS/AS intends to transmit data (e.g., non-IP data) to the UE via theSCEF.

When the serving node (e.g., MME/SGSN or C-SGN) detects change of theserving node of the UE during a tracking area update/routing area updateprocedure (i.e., when the serving node which has received a TAU requestmessage or an RAU request message is different from the old node), andconnection for transmission/reception of non-IP data via the servicecapability exposure function (SCEF) is configured for the UE, theserving node notifies the SCEF of change of the serving node.

Here, a case in which the type of PDN connection currently configuredfor the UE through the procedure of FIG. 18 is “non-IP” and the PDNconnection is established via the SCEF may correspond to an example ofthe case in which connection for transmission/reception of non-IP datavia the SCEF is configured for the UE. In this case, whether the PDNconnection is established via the SCEF may be determined based onwhether the Invoke SCEF Selection indicator is included (i.e., set) asshown in Table 3 prior to subscription information corresponding to anAPN about the PDN connection.

Alternatively, a case in which a small data transmission event or amonitoring event for SDT is configured in the serving node maycorrespond to an example of the case in which connection fortransmission/reception of non-IP data via the SCEF is configured for theUE. That is, when an SDT event or a monitoring event for SDT isconfigured in the serving node according to the procedure of FIG. 13,the serving node may notify the SCEF of change of the serving node whenthe serving node is changed.

Alternatively, a case in which an SDT monitoring event is configured androuting information update is configured for the SCEF with respect toserving node change may correspond to an example of the case in whichconnection for transmission/reception of non-IP data via the SCEF isconfigured for the UE. That is, referring to FIG. 13, the SCS/AS mayinclude information indicating reporting of serving node change in themonitoring request message and transmit the monitoring request messageincluding the indication information to the SCEF in step 1. In addition,the SCEF may include information indicating reporting of serving nodechange in the monitoring request message and transmit the monitoringrequest message including the indication information to the HSS in step3. Further, the HSS may include information indicating reporting ofserving node change in the Insert Subscriber Data Request message andtransmit the message including the indication information to the servingnode in step 5. Upon reception of the indication information, theserving node may notify the SCEF of change of the serving node when theserving node is changed.

Hereinafter, a method of reporting change of a serving node to the SCEFwill be described.

FIG. 20 shows a tracking area update procedure in a wirelesscommunication system to which the present invention is applicable.

The TAU procedure may be performed when UE entry into a new trackingarea (TA) which is not included in a tracking area identity (TAI) listregistered with a network is detected, a periodic TAU timer expires, ortemporary identity used in next update (TIN) indicates packet-temporarymobile subscriber identity (P-TMSI) when a UE reselects E-UTRAN.

FIG. 20 illustrates a case of an inter-MME TAU procedure.

1-3. When a TAU timer of a UE in an ECM-IDLE state expires or the UEmoves to another tracking area, a TAU procedure for reporting a trackingarea (TA) to an MME is triggered.

The UE starts the TAU procedure by transmitting a TAU request message tothe MME.

The TAU request message is included in an RRC Connection Setup Completemessage and delivered in RRC connection, and included in an initial UEmessage and delivered in S1 signaling connection.

When the UE needs to use eDRX, the UE includes eDRX parameterinformation in the TAU request message even when eDRX parameters havebeen negotiated.

4. When the MME which has received the TAU request message differs fromthe old node (i.e., MME or SGSN) (i.e., when the MME has been changed),a new MME transmits a context request message to the old MME/SGSN inorder to acquire user information (or UE context) from the old MME/SGSN.

5. When the context request message is transmitted to the old MME/SGSN,the old MME/SGSN responds to the context request message using a contextresponse message. The context response message may include UE context.

6. The UE, the new MME and an HSS perform an authentication function anda security (or ciphering) procedure.

The new MME determines whether to relocate an S-GW. When the old S-GWcannot provide a service to the UE any more, the S-GW is relocated. Inaddition, the new MME may determine relocation of the S-GW when a newS-GW is expected to provide the service to the UE for a longer timeand/or a P-GW path is expected to be more suitable for the UE or the newS-GW is collocated with a P-GW.

7. When the MME selects a new S-GW, the MME transmits a Create SessionRequest message to the selected new S-GW for each PDN connection.

8. The new S-GW transmits a Modify Bearer Request message to the P-GWfor each PDN connection as necessary.

9a. The P-GW may perform an IP connectivity access network (IP-CAN)session modification procedure with a PCRF as necessary.

9. Upon reception of the Modify Bearer Request message from the newS-GW, the P-GW transmits a Modify Bearer Response message to the newS-GW in response to the Modify Bearer Request message.

10. The new S-GW updates the bearer context thereof. Accordingly, thenew S-GW may route a bearer PDU to the P-GW when receiving the bearerPDU from an eNB.

The new S-GW transmits a Create Session Response message to the new MMEin response to the Create Session Request message.

11. The new MME transmits a Context Acknowledge message to the oldMME/SGSN.

When the MME selects a new S-GW, the MME delivers S-GW change indicationinformation to the old MME/SGSN through the Context Acknowledge message.The S-GW change indication information indicates that the new S-GW hasbeen selected.

12. The new MME transmits an Update Location Request message to the HSS.

Here, the new MME may check presence or absence of subscriptioninformation about the UE is present, and when the subscriptioninformation about the UE is not present, transmit the Update LocationRequest message to the HSS.

13. The HSS transmits a Cancel Location message to the old MME/SGSN.

14. The old MME/SGSN transmits a Cancel Location Acknowledge message tothe HSS in response to the Cancel Location message.

15. When the old SGSN receives the Context Acknowledge message and theUE is connected through an Iu interface, the old SGSN transmits an IuRelease Command message to an RNC.

16. The RNC transmits an Iu Release Complete message to the old SGSN inresponse to the Iu Release Command message.

17. The HSS transmits an Update Location Acknowledge message to the newMME in response to the Update Location Request message.

The Update Location Acknowledge message may include the subscriptioninformation about the UE.

18. When S-GW change indication is received in the Context Acknowledgemessage of step 11, the old MME/SGSN cancels MME or SGSN EPS bearerresources by transmitting a Delete Session Request message to the oldS-GW.

19. The old S-GW transmits a Delete Session Response message to the oldMME/SGSN in response to the Delete Session Request message.

20. The new MME transmits a TAU Accept message to the UE. Here, when thenew MME allocates new globally unique temporary identity (GUTI) to theUE, the allocated GUTI may be included in the TAU Accept message.

When the UE has included the eDRX parameter information in the TAUrequest message, the MME includes the eDRX parameter information in theTAU Accept message if the MME determines that eDRX is enabled.

When the TAU Accept message is received and ISR activated indication isnot included in the TAU Accept message, the UE sets TIN to globallyunique temporary identity (GUTI).

21. When the GUTI is included in the TAU Accept message, the UEtransmits a TAU Complete message to the MME in response to the TAUAccept message.

When a serving node (e.g., MME/SGSN or C-SGN) needs to notify the SCEFof change of the serving node, the serving node may transmit the UpdateLocation message for reporting change of the serving node to the SCEF inthe procedure of FIG. 20. This will be described below with reference tothe drawing.

FIG. 21 shows a serving node relocation method according to anembodiment of the present invention.

Referring to FIG. 21, steps 1 to 12 of FIG. 20 are performed.

12a. When the serving node of the UE is changed (i.e., when the servingnode which has received the TAU/RAU request message differs from the oldnode) and connection for transmission/reception of non-IP data via theSCEF is configured for the UE, the serving node transmits the UpdateLocation message to the SCEF to notify the SCEF of change of the servingnode.

For example, when an SDT monitoring event configured for the UE ispresent in the MME and notification about serving node change isconfigured by the operator, the serving node may transmit the UpdateLocation message to the SCEF in order to indicate serving node change(i.e., MME identifier and C-SGN identifier).

Alternatively, when the type of PDN connection currently set between theUE and the SCS/AS through the procedure of FIG. 18 is “non-IP” and thePDN connection is established via the SCEF, the serving node maytransmit the Update Location message to the SCEF in order to indicateserving node change (i.e., MME identity and C-SGN identity).

Here, the serving node may determine whether connection fortransmission/reception of non-IP data through the SCEF has beenconfigured between the UE and the SCS/AS using UE context receivedthrough the Context Response message from the old node. Morespecifically, the serving node may determine that connection fortransmission/reception of non-IP data has been configured for the UE byreceiving UE context including information about non-IP PDN connectionfrom the old node. In addition, the serving node may determine thatconnection for transmission/reception of non-IP data has been configuredthrough the SCEF when the subscription information corresponding to theAPN with respect to the PDN connection, received from the HSS, includesInvoke SCEF Selection.

12b. The serving node receives an Update Location Acknowledgementmessage in response to the Update Location message. That is, the SCEFacknowledges successful location update.

Then, steps 13 to 21 of FIG. 20 are performed.

Although FIG. 21 shows that steps 12a and 12b are performed after steps1 to 12 and then steps 12 to 21 are performed, steps 12a and 12b may beperformed in a different order. Furthermore, steps 12a and 12b may beperformed after completion of the TAU/RAU procedure.

In addition, in the case of a TAU/RAU procedure for CIoT, interactionwith the P-GW, PCRF and the like in the conventional TAU/RAU proceduremay be skipped.

As described above, the SCEF recognizes the newest serving node and thusnon-IP data transmission can be performed without loss in mobiletermination call transmission.

In high latency communication (HLcom), UE reachability and availabilityafter DDN failure monitoring events may be used for stabilized mobileterminated (MT) data transmission of the SCS/AS. In this case, when theMME recognizes serving node change, the MME may notify the SCEF ofserving node identity (MME identity) along with UE reachability.

This may be added at the request of the SCS/AS or SCEF or always addedfor non-IP data transmission. That is, the MME may indicate identity ofthe current serving node (e.g., MME identity, C-SGN identity) along withUE reachability when indicating the UE reachability.

In general, HLcom has been used for IP packet transmission through SGiinterface, but it is necessary to apply the HLcom function to a case inwhich the MME transmits/receives data to/from the SCEF as non-IP packettransmission is required in Release-13.

However, if the SCS/AS configures a UE reachability monitoring event forDL packet transmission and then is informed of reachability, but aserving node to which DL packets need to be transmitted has beenchanged, the old node is required to transmit data. Consequently, datatransmission may fail.

Accordingly, it is necessary to include serving node information (i.e.,serving node identity) in a monitoring indication message and totransmit the message including the serving node information to the SCEFwhen the event is reported (i.e., the monitoring indication message istransmitted). This will be described below with reference to thedrawing.

FIG. 22 shows a serving node relocation method according to anembodiment of the present invention.

1 a. A node (i.e., MME/SGSN (in the case of 1 a)) in which a monitoringevent is configured detects the monitoring event.

2a. The MME/SGSN transmits a monitoring indication message (an SCEFreference ID, a monitoring event report and serving node identity) tothe SCEF. When the monitoring event configuration has been triggered bya one-time monitoring request, the monitoring event configuration iscleared by the MME/SGSN when this step is completed. If the MME/SGSN hasa maximum number of reports stored for this monitoring task, theMME/SGSN decreases the maximum number of reports by 1.

Here, serving node information (i.e., serving node identity) may beincluded in the monitoring indication message and transmitted each time.When the SCS/AS requests indication of serving node change (i.e.,indication of serving node change to the SCEF and/or the SCS/AS isrequested), the monitoring indication message may include the servingnode information. Alternatively, the monitoring indication message mayinclude serving node information only when the serving node when theprevious monitoring event is reported is changed.

2b. The HSS transmits the monitoring indication message (SCEF ReferenceID and monitoring event report to the SCEF. If the monitoring eventconfiguration is triggered by a one-time monitoring request, themonitoring event configuration is cleared by the HSS when this step iscompleted. If the HSS has a maximum number of reports stored for thismonitoring task, the HSS decreases the value by 1.

3. The SCEF retrieves a related SCS/AS reference ID along with amonitoring destination address or an SCS/AS address as a destination fortransmission of the monitoring indication message using the SCEFreference ID. The SCEF transmits a monitoring indication message (SCS/ASreference ID, external ID or MSISDN and monitoring Information) to theidentified destination.

When the number of continuous monitoring requests reaches the maximumnumber of reports or in the case of a one-time monitoring request, theSCEF requests that the HSS (in the case of a monitoring event configuredthrough the HSS) or MME(s)/SGSN(s) (in the case of a monitoring eventdirectly configured by the MME/SGSN) clear the related monitoring eventconfiguration and the monitoring event configuration according to steps3 to 8 in the procedure of FIG. 13.

That is, when the MME transmits the monitoring indication message as instep 2a, the MME transmits the serving node identity (e.g.,MME/SGSN/C-SGN identity) along with the monitoring indication message tothe SCEF. Then, the SCEF may update information of the previous servingnode and transmit MT data (e.g., Non-IP data and small data) to thenewest serving node.

The operation of additionally transmitting the serving node identity asdescribed above may also be performed when a UE reachability event or anavailability after DDN failure monitoring event is used.

Furthermore, when packet data is transmitted to the MME/C-SGN throughthe SCEF instead of SGi, the operation of additionally transmittingserving node identity may also be performed.

FIG. 23 shows a serving node relocation method according to anembodiment of the present invention.

Referring to FIG. 23, a serving node (e.g., MME/SGSN or C-SGN) transmitsan Update Location message to the SCEF (S2301).

Here, the Update Location message may be transmitted during the TAUprocedure as shown in FIG. 21, but may be transmitted after the TAUprocedure is completed.

In other words, the UE performs a successful TAU/RAU procedure and thenew serving node receives the Invoke SCEF Selection indicator andsubscription information for non-IP PDN/PDP connection to an APNcorrelated with the related SCEF ID (identifier). Then, the procedure ofFIG. 23 may be performed.

In the following description, the new node shown in FIG. 23 is referredto as a first serving node and the old node is referred to as a secondserving node.

Here, after the first serving node receives a TAU request message fromthe UE, the first serving node may transmit an Update Location Requestto the home subscriber server (HSS) when the first serving node differsfrom the second serving node.

On the other hand, when the first serving node differs from the secondserving node and connection for transmission/reception of non-IP datavia the SCEF is configured for the UE, the first serving node maytransmit an Update Location message to the SCEF.

That is, the first serving node may not transmit the Update Locationmessage to the SCEF when connection for transmission/reception of non-IPdata is not configured for the UE even when serving nodes change due tothe TAU procedure, differently from the Update Location Requesttransmitted to the HSS.

When the first serving node differs from the second serving node duringthe TAU procedure, the first serving node may transmit a context requestmessage to the second serving node in order to retrieve UE context. Inaddition, the first serving node may receive a context response messageincluding the UE context from the second serving node in response to thecontext request message. Here, the first serving node may determinewhether connection for transmission/reception of non-IP data via theSCEF has been configured for the UE using the UE context.

More specifically, when the type of PDN connection between the UE and apacket data network (PDN) is “non-IP” and subscription informationcorresponding to the PDN connection includes the Invoke SCEF Selectionindicator, it can be determined that connection fortransmission/reception of non-IP data via the SCEF has been configuredfor the UE.

In other words, when subscription information corresponding to a defaultAPN for “non-IP” PDN type or an APN requested by the UE includes theInvoke SCEF Selection indicator, the new serving node generates PDN/PDPconnection to the SCEF using previously allocated EBI (refer to FIG.18). The new serving node may perform this operation by transmitting theUpdate Location message to the SCEF.

The Update Location message may include at least one of user identity,EBI, SCEF ID, APN, serving PLMN ID, and international mobile stationequipment identity (IMEISV).

When the SCEF has received the reachable for NIDD flag for the UE fromthe old serving node but has not received an NIDD Submit Indicationmessage from the old serving node and is buffering non-IP data, the SCEFmay perform the procedure shown in FIG. 19 from step 7.

The reachable for NIDD flag refers to a flag indicating that the MMEnotifies the SCEF of UE reachability when the MME determines that the UEis reachable.

If an IWK-SCEF receives the Update Location message from the servingnode, the IWK-SCEF may deliver the message to the SCEF.

The first serving node receives an Update Location Acknowledgementmessage from the SCEF in response to the Update Location message(S2302).

The Update Location Acknowledgement message may correspond to a messagefor confirming establishment of PDN connection to the SCEF for the UE.

The SCEF may generate an SCEF EPS bearer context for a user identifiedthrough user identity. Here, the SCEF EPS bearer context may include atleast one of user identity, an APN, an EBI, an NIDD charging ID, servingnode information (a serving node address used for SCEF connection, aserving PLMN ID (mobile country code (MCC)+mobile network code (MNC) fora serving PLMN) and IMEISV.

The Update Location Acknowledgement message may include at least one ofthe user identity, the EBI, the SCEF ID, cause and the NIDD charging ID.

If the IWK-SCEF receives the Update Location Acknowledgement messagefrom the SCEF, the IWK-SCEF may deliver the message to the serving node.

Thereafter, when the first serving node receives non-IP data to betransmitted to the corresponding UE from the SCEF, the first servingnode encrypts the non-IP data, performs integrity protection and thentransmits the non-IP data to an eNB using a NAS PDU delivered through adownlink S1-AP message. The NAS PDU including non-IP data is transmittedto the UE through a downlink RRC message.

Similarly, the UE transmits the NAS PDU including the non-IP data to theeNB through an uplink RRC message. The eNB transmits the NAS PDUincluding the non-IP data to the first serving node in an uplink S1-APmessage.

The above-described serving node relocation procedure may be appliedwhen T6a/T6b PDN/PDP connection is configured for a UE which hasperformed a successful TAU procedure for a new MME or a successful RAUprocedure for a new SGSN.

Meanwhile, the terms “Update Location message” and “Update Location Ackmessage” are exemplary and different terms may be used. For example, theUpdate Location message may be referred to as an Update Serving NodeInformation Request message and the Update Location Ack message may bereferred to as an Update Serving Node Information Response message.

Overview of Devices to Which the Present Invention Can Be Applied

FIG. 24 illustrates a block diagram of a communication device accordingto one embodiment of the present invention.

With reference to FIG. 24, a wireless communication system comprises anetwork node 2410 and a plurality of UEs 2420.

A network node 2410 comprises a processor 2411, memory 2412, andcommunication module 2413. The processor 2411 implements proposedfunctions, processes and/or methods proposed through FIG. 1 to FIG. 23.The processor 2411 can implement layers of wired/wireless interfaceprotocol. The memory 2412, being connected to the processor 2411, storesvarious types of information for driving the processor 2411. Thecommunication module 2413, being connected to the processor 2411,transmits and/or receives wired/wireless signals. Examples of thenetwork node 2410 include an eNB, MME, HSS, SGW, PGW, application serverand so on. In particular, in case the network node 2410 is an eNB, thecommunication module 2413 can include a Radio Frequency (RF) unit fortransmitting/receiving a radio signal.

The UE 2420 comprises a processor 2421, memory 2422, and communicationmodule (or RF unit) 2423. The processor 2421 implements proposedfunctions, processes and/or methods proposed through FIG. 1 to FIG. 23.The processor 2421 can implement layers of wired/wireless interfaceprotocol. The memory 2422, being connected to the processor 2421, storesvarious types of information for driving the processor 2421. Thecommunication module 2423, being connected to the processor 2421,transmits and/or receives wired/wireless signals.

The memory 2412, 2422 can be installed inside or outside the processor1411, 1421 and can be connected to the processor 2411, 2421 throughvarious well-known means. Also, the network node 2410 (in the case of aneNB) and/or the UE 2420 can have a single antenna or multiple antennas.

FIG. 25 illustrates a block diagram of a wireless communicationapparatus according to an embodiment of the present invention.

Particularly, in FIG. 25, the UE described above FIG. 24 will beexemplified in more detail.

Referring to FIG. 25, the UE includes a processor (or digital signalprocessor) 2510, RF module (RF unit) 2535, power management module 2505,antenna 2540, battery 2555, display 2515, keypad 2520, memory 2530,Subscriber Identification Module (SIM) card 2525 (which may beoptional), speaker 2545 and microphone 2550. The UE may include a singleantenna or multiple antennas.

The processor 2510 may be configured to implement the functions,procedures and/or methods proposed by the present invention as describedin FIG. 1-23. Layers of a wireless interface protocol may be implementedby the processor 2510.

The memory 2530 is connected to the processor 2510 and storesinformation related to operations of the processor 2510. The memory 2530may be located inside or outside the processor 2510 and may be connectedto the processors 2510 through various well-known means.

A user enters instructional information, such as a telephone number, forexample, by pushing the buttons of a keypad 2520 or by voice activationusing the microphone 2550. The microprocessor 2510 receives andprocesses the instructional information to perform the appropriatefunction, such as to dial the telephone number. Operational data may beretrieved from the SIM card 2525 or the memory module 2530 to performthe function. Furthermore, the processor 2510 may display theinstructional and operational information on the display 2515 for theuser's reference and convenience.

The RF module 2535 is connected to the processor 2510, transmits and/orreceives an RF signal. The processor 2510 issues instructionalinformation to the RF module 2535, to initiate communication, forexample, transmits radio signals comprising voice communication data.The RF module 2535 comprises a receiver and a transmitter to receive andtransmit radio signals. An antenna 2540 facilitates the transmission andreception of radio signals. Upon receiving radio signals, the RF module2535 may forward and convert the signals to baseband frequency forprocessing by the processor 2510. The processed signals would betransformed into audible or readable information outputted via thespeaker 2545.

The aforementioned embodiments are achieved by combination of structuralelements and features of the present invention in a predeterminedmanner. Each of the structural elements or features should be consideredselectively unless specified separately. Each of the structural elementsor features may be carried out without being combined with otherstructural elements or features. Also, some structural elements and/orfeatures may be combined with one another to constitute the embodimentsof the present invention. The order of operations described in theembodiments of the present invention may be changed. Some structuralelements or features of one embodiment may be included in anotherembodiment, or may be replaced with corresponding structural elements orfeatures of another embodiment. Moreover, it will be apparent that someclaims referring to specific claims may be combined with another claimsreferring to the other claims other than the specific claims toconstitute the embodiment or add new claims by means of amendment afterthe application is filed.

The embodiments of the present invention may be achieved by variousmeans, for example, hardware, firmware, software, or a combinationthereof. In a hardware configuration, the methods according to theembodiments of the present invention may be achieved by one or moreApplication Specific Integrated Circuits (ASICs), Digital SignalProcessors (DSPs), Digital Signal Processing Devices (DSPDs),Programmable Logic Devices (PLDs), Field Programmable Gate Arrays(FPGAs), processors, controllers, microcontrollers, microprocessors,etc.

In a firmware or software configuration, the embodiments of the presentinvention may be implemented in the form of a module, a procedure, afunction, etc. Software code may be stored in a memory unit and executedby a processor. The memory unit may be located at the interior orexterior of the processor and may transmit data to and receive data fromthe processor via various known means.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

INDUSTRIAL APPLICABILITY

The present invention is applied to a 3GPP LTE/LTE-A system is primarilydescribed, but can be applied to various wireless communication systemsin addition to the 3GPP LTE/LTE-A system.

1-10. (canceled)
 11. A method for relocating, by a first serving node, aserving node in a wireless communication system, the method comprising:receiving a first message related to a location update of a userequipment (UE) from the UE; transmitting a second message for requestingthe location update of the UE to a first network node, when the firstserving node having received the first message is different from asecond serving node that is an old node; and transmitting a thirdmessage to a second network node in response to the second message, whenthe first serving node is different from the second serving node that isthe old node and a connection for transmitting/receiving non-Internetprotocol (non-IP) data via the second network node is configured for theUE.
 12. The method of claim 11, further comprising: transmitting arequest message to the second serving node in order to retrieve a UEcontext, when the first serving node is different from the secondserving node that is the old node; and receiving a response messageincluding the UE context from the second serving node in response to therequest message, wherein whether the connection fortransmitting/receiving non-IP data is configured for the UE isdetermined using the UE context.
 13. The method of claim 12, wherein itis determined that the connection for transmitting/receiving non-IP datavia the second network node is configured for the UE, when the type of aconnection between the UE and a data network is non-IP, and subscriptioninformation corresponding to the connection between the UE and the datanetwork includes information related to selection the second networknode
 14. The method of claim 11, wherein the third message istransmitted to the second network node, when notification to the secondnetwork node for a relocation of the serving node is configured in thefirst serving node.
 15. The method of claim 11, further comprisingreceiving an acknowledgement message for acknowledging the locationupdate from the second network node in response to the third message.16. The method of claim 11, further comprising including non-IP data tobe transmitted to the UE in a data unit for non-access stratum (NAS) andtransmitting the data unit for the NAS including the non-IP data to theUE when the non-IP data is received from the second network node.
 17. Afirst serving node for relocating a serving node in a wirelesscommunication system, the node comprising: a transceiver fortransmitting/receiving signals; and a processor for controlling thetransceiver, wherein the processor is configured: to receive a firstmessage related to a location update of a user equipment (UE) from theUE; to transmit a second message for requesting the location update ofthe UE to a first network node, when the first serving node havingreceived the first message is different from a second serving node thatis an old node; and to transmit a third message to a second network nodein response to the second message, when the first serving node isdifferent from the second serving node that is the old node and aconnection for transmitting/receiving non-Internet protocol (non-IP)data via the second network node is configured for the UE.
 18. The firstserving node of claim 17, wherein the processor is configured: totransmit a request message to the second serving node in order toretrieve a UE context, when the first serving node is different from thesecond serving node that is the old node; and to receive a responsemessage including the UE context from the second serving node inresponse to the request message, wherein whether the connection fortransmitting/receiving non-IP data is configured for the UE isdetermined using the UE context.
 19. The first serving node of claim 18,wherein it is determined that the connection for transmitting/receivingnon-IP data via the second network node is configured for the UE, whenthe type of a connection between the UE and a data network is non-IP,and subscription information corresponding to the connection between theUE and the data network includes information related to selection thesecond network node.
 20. The first serving node of claim 17, wherein theprocessor is configured to receive an acknowledgement message foracknowledging the location update from the second network node inresponse to the third message.